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Circulation. 1996;93:356-364

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(Circulation. 1996;93:356-364.)
© 1996 American Heart Association, Inc.

Articles

Increased Release of NO During Ischemia Reduces Myocardial Contractility and Improves Metabolic Dysfunction

Presented in part at the 44th Annual Scientific Session of the American College of Cardiology, New Orleans, La, March 19-22, 1995.

Koichi Node, MD; Masafumi Kitakaze, MD; Hiroaki Kosaka, MD; Kazuo Komamura, MD; Tetsuo Minamino, MD; Michitoshi Inoue, MD; Michihiko Tada, MD ; Masatsugu Hori, MD; Takenobu Kamada, MD

From the First Department of Medicine, the First Department of Physiology (H.K.), and the Department of Pathophysiology (M.T.), Department of Information Science, Osaka University School of Medicine, Osaka, Japan.

Correspondence to Masafumi Kitakaze, MD, PhD, First Department of Medicine, Osaka University School of Medicine, 2-2 Yamadaoka, Suita 565, Osaka, Japan.


*    Abstract
up arrowTop
 *Abstract
down arrowIntroduction
 down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Background We have reported that myocardial ischemia increases nitric oxide (NO) production. Several lines of evidence suggest that NO reduces myocardial contraction. Therefore, we tested whether endogenous NO decreases the inotropic response of the ischemic myocardium and whether endogenous NO is beneficial in the metabolic function of ischemic myocardium.

Methods and Results The left anterior descending coronary artery was perfused with blood from the left carotid artery in 72 dogs. An infusion of NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthase, did not affect fractional shortening (FS) under nonischemic conditions. After reduction of perfusion pressure so that coronary blood flow decreased to 60% of the control value, FS of the perfused area decreased, and intravenous infusion of isoproterenol increased FS. Before and during intravenous infusion of isoproterenol under conditions of coronary hypoperfusion, FS was significantly increased in the L-NAME group compared with the untreated group. Both lactate extraction ratio and the pH in coronary venous blood were significantly lower in the L-NAME–treated group than in the untreated group during coronary hypoperfusion. Infusion of L-arginine prevented the effects of L-NAME in the ischemic myocardium.

Conclusions These results indicate that endogenous NO reduces myocardial contractile function and improves myocardial metabolic function in the ischemic heart. The myocardial energy–sparing effect as well as coronary vasodilation due to NO may be beneficial to the ischemic myocardium.


Key Words: myocardial contraction • ischemia • L-NAME • nitric oxide • receptors, adrenergic


*    Introduction
up arrowTop
 up arrowAbstract
 *Introduction
down arrowMethods
down arrowResults
down arrowDiscussion
down arrowReferences
 
NO is produced in the endothelium1 2 and other tissues of the heart, where it acts as both a paracrine and autocrine autacoid. Thus, NO activates guanylate cyclase in ventricular myocytes as well as in coronary smooth muscle cells. Recent studies with cardiomyocytes, isolated papillary muscles, and isolated hearts suggest that NO and other interventions that increase cGMP concentration may influence myocardial contractility.3 4 5 6 7 8 9 Negative inotropic effects of cytokines on the heart were reduced by an inhibitor of NOS, and production of NO in septic shock decreases myocardial contractility,10 11 12 13 14 suggesting that an enhanced release of NO may reduce myocardial contractility. Myocardial ischemia increases NO production in the heart.15 16 17 18 19 20 However, it is not clear whether NO released from the ischemic myocardium contributes to the reduction of myocardial contractility. If NO decreases myocardial contractility in the ischemic heart, it also remains to be determined whether this effect is mediated directly, by activation of guanylate cyclase, or indirectly, by inhibition of norepinephrine release from sympathetic nerve endings. Finally, it is not known whether the NO-induced decreases in contractility are beneficial or deleterious for the ischemic myocardium.

We have tested the hypothesis that endogenous NO released from the ischemic myocardium directly reduces the inotropic response to ß-adrenergic receptor stimulation and exposure to Ca2+. Regional myocardial contractile and metabolic functions during infusions of isoproterenol and CaCl2 were assessed in ischemic canine hearts when the amount of endogenous NO was decreased by L-NAME, an inhibitor of NOS. We also examined whether the concomitant administration of L-arginine reversed any observed effect of L-NAME. To clarify whether the reduction in myocardial contractility is due to direct myocardial effects of NO or to inhibition of norepinephrine release, we performed identical procedures in chemically denervated hearts. Finally, we examined the effect of L-NAME administration on anaerobic myocardial metabolism during coronary hypoperfusion.


*    Methods
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 up arrowAbstract
 up arrowIntroduction
 *Methods
down arrowResults
down arrowDiscussion
down arrowReferences
 
Instrumentation
Seventy-two mongrel dogs (body weight, 15 to 23 kg) were anesthetized with intravenous pentobarbital sodium (30 mg/kg body wt), intubated with a cuffed endotracheal tube, and ventilated with room air mixed with oxygen (1 to 2 L/min) with a respirator. A left thoracotomy was performed through the fifth intercostal space, and the heart was suspended in a pericardial cradle. After the intravenous administration of heparin 500 U/kg, a proximal portion of the LAD was cannulated and perfused with blood through an extracorporeal tube from the left carotid artery. An electromagnetic flow probe (FF-050T, Nihon Kohden) was attached to the bypass tube for measurement of CBF. CPP was measured at the proximal portion of the cannula. The femoral artery was cannulated to sample the blood for the reference to obtain the absolute value of the regional myocardial blood flow. For blood sampling, a small, short tube (diameter, 1 mm; length, 7 cm) was inserted into the epicardial vein at the center of the perfused area, and the drained coronary venous blood was returned to the jugular vein. A miniature pressure transducer (model P-5, Konigsberg) was inserted into the left ventricular cavity through a stab incision at the apex of the left ventricle. A pair of ultrasonic crystals (5 MHz, 2 mm in diameter; Schuessler) was implanted in the left ventricular anterior wall in the endomyocardial segment in the center of the perfused area to measure segment length. Hemodynamic parameters were recorded on a multichannel recorder (Rm-6000, Nihon Kohden). We calculated FS from the equation FS=[(EDL-ESL)/EDL]x100%, where EDL and ESL are end-diastolic and end-systolic segment lengths, respectively. Heart rate was 141±2 beats per minute in the intact heart and 104±2 beats per minute in the denervated heart.

The preparation of the experiment setup took 30 to 40 minutes. The hemodynamic and metabolic parameters were stable for 3 hours: There was no change in CPP (101±3 versus 100±2 mm Hg), CBF (88±3 versus 86±2 mL·100 g-1·min-1), LER (22.4±3.9% versus 21.7±2.5%), pH in the coronary venous blood (7.38±0.02 versus 7.36±0.03), or FS (25.2±1.9% versus 23.8±2.4%) between 1 and 3 hours after the experimental setup in the preliminary study (n=5).

Experimental Protocols
Protocol 1: Effect of L-NAME on the Inotropic Response to ß-Adrenergic Stimulation in the Ischemic Myocardium
Twenty-seven dogs were subjected to this protocol. After hemodynamic stabilization, left ventricular pressure, segment length in the perfused area, CPP, and CBF were measured. Coronary arterial and venous blood was sampled by syringes for blood gas analysis and determination of lactate and nitrate plus nitrite concentrations. With an occluder attached at the extracorporeal bypass tube, CPP was reduced so that CBF decreased to 60% of the control value. After the low CPP was set, the occluder was manually adjusted to maintain CPP constant at the set level. In 9 dogs (untreated group), these procedures were performed without treatment with L-NAME. In a second group of 9 dogs (L-NAME group), the effect of endogenous NO on the ischemic myocardium was prevented by continuous intracoronary administration of L-NAME. L-NAME 10 µg·kg-1·min-1 was administered into the extracorporeal bypass tube 10 minutes before coronary hypoperfusion. In the third group of 9 dogs (L-NAME+L-arginine group), L-arginine 1 mg·kg-1·min-1 was infused into the bypass tube in addition to L-NAME 10 µg·kg body wt-1·min-1 to determine whether exogenous L-arginine can restore the effects of L-NAME. The infusions of L-arginine and L-NAME began 5 and 10 minutes, respectively, before the onset of hypoperfusion. Coronary hemodynamic and metabolic parameters were measured 1 minute before the onset of hypoperfusion. Five minutes after the onset of coronary hypoperfusion, two doses of isoproterenol (75 and 150 ng·kg-1 ·min-1) were infused intravenously. Measurements of the hemodynamic and metabolic parameters were performed before and 5 minutes after the infusion of each dose of isoproterenol. In a preliminary study, we confirmed that the hemodynamic and metabolic parameters are stabilized within 4 minutes after the onset of infusion of isoproterenol. For the assessment of the Endo/Epi flow ratio, microspheres were injected into the left atrium before and during coronary hypoperfusion with and without an infusion of isoproterenol 150 ng·kg-1·min-1 in each group.

Protocol 2: Effect of L-NAME on the CaCl2-Induced Inotropic Response of the Ischemic Myocardium
Twenty-seven dogs were divided into three groups of 9 each and subjected to the same procedures as outlined in protocol 1 with the exception that, instead of the intravenous administration of isoproterenol, two doses (1.5 and 3.0 µmol·kg-1 ·min-1) of CaCl2 (Wako) dissolved in saline were infused into the LAD via the bypass tube. The Endo/Epi flow ratio was measured before and during coronary hypoperfusion with and without infusion of CaCl2 (3.0 µmol·kg-1·min-1) in each group.

Protocol 3: Effect of L-NAME on the ß-Adrenergic Receptor–Mediated Inotropic Response of the Ischemic Myocardium in Chemically Denervated Hearts
Eighteen dogs were divided into three groups of 6 and, after chemical denervation of the heart, were subjected to the procedures described in protocol 1. Systemic chemical sympathectomy was performed with an intravenous injection of 6-hydroxydopamine 50 mg/kg 5 days before the experiment. Deleterious side effects of 6-hydroxydopamine were prevented by previous injections of propranolol 1 mg/kg and phentolamine 1 mg/kg; three fractional doses of 6-hydroxydopamine (10, 20, and 20 mg/kg) were administered over a 24-hour period.21 Dogs were killed immediately after the experiment, and myocardial tissue from the perfused area was sampled for the measurement of norepinephrine content. Norepinephrine contents of the myocardium of systemically denervated and innervated dogs were 11±3 and 366±28 pg/mg tissue (P<.05), respectively.

Measurement of Regional Coronary Blood Flow
Regional myocardial blood flow was determined by the microsphere technique as previously described.18 19 Nonradioactive microspheres (Sekisui) made of inert plastic and labeled with bromine, niobium, or zirconium were used in the present study. Specific gravities were 1.34 for bromine, 1.32 for niobium, and 1.36 for zirconium. The microspheres were suspended in isotonic saline with 0.01% Tween 80 to prevent aggregation, ultrasonicated for 5 minutes, and mixed vigorously for 5 minutes immediately before injection. Approximately 1 mL of the microsphere suspension (2x106 to 4x106 microspheres) was injected into the left atrium, followed by several warm (37°C) saline flushes. Immediately after the microsphere administration, a reference blood sample was taken from the femoral artery at a constant rate of 8 mL/min for 2 minutes. The x-ray fluorescence activities of the stable heavy elements were measured by a wavelength dispersive spectrometer (PW 1480, Phillips Co, Ltd), as described previously.22 23 Because the fluorescence is characteristic for each element when the microspheres are irradiated by the primary x-rays, it is therefore possible to quantify the x-ray fluorescence of several differently labeled microspheres in a mixture. Myocardial blood flow was calculated according to the formula times reference flow divided by reference counts and was expressed in milliliters per minute per gram of tissue wet mass.

Chemical Analysis
The partial pressure of oxygen, hemoglobin content, and pH of blood were measured with a Radiometer ABL-30. The coronary {Delta}AVO2 (mL/dL) was determined as the difference between coronary arterial and venous oxygen contents. MO2 (mL·100 g-1·min-1) was calculated from CBF (mL·100 g-1·min-1) multiplied by {Delta}AVO2. For measurement of lactate concentration, blood (1 mL) was rapidly sampled and centrifuged. Lactate concentration in 0.2 mL of the supernatant was measured by enzyme assay, and LER was obtained by dividing the coronary arteriovenous difference in lactate concentration by the arterial lactate concentration and multiplying by 100%.

NO Measurement
Blood was collected into heparinized test tubes and centrifuged within 30 seconds for 5 minutes at 2000g. The plasma fraction was diluted 1:1 with nitrite- and nitrate-free distilled water, and 400 µL of the diluted sample was centrifuged at 2000g in an Ultrafree MC microcentrifuge device (Millipore) to remove substances of molecular weight >10 kD. The filtrate was passed through a copper-plated cadmium column to reduce nitrate to nitrite and reacted with the Griess reagent, and absorbance was measured at 540 nm.24 25 26 27 This value represented the total amount of plasma NO end products, ie, nitrate plus nitrite. Coronary arteriovenous differences in nitrate plus nitrite concentration [{Delta}AV(NO)] reflect the amount of NO released from the myocardium.

Norepinephrine Measurement
The method of norepinephrine measurement has been described previously.28 Myocardial tissue from the area of the LAD was sampled within 5 seconds and frozen in liquid nitrogen. The frozen tissue was stored at -80°C for <1 week, and then homogenized in a solution containing EDTA (0.1 mol/L), NaHSO3 (1 mol/L), and HClO3 (0.05 mol/L). The homogenate was centrifuged at 2000g for 10 minutes, and norepinephrine in the supernatant was adsorbed onto alumina and separated by high-performance liquid chromatography (LC-3A pump and Zpax-SCX column, Shimazu Seisakusho). Norepinephrine content was determined spectrofluorometrically by the trihydroxyindole method (Shimazu spectrofluorophotometer RF-500LCA). The sensitivity of the assay is 10 pg/mL sample, and the intra-assay coefficient of variation is 6.8%.28

Statistical Analysis
Data are presented as mean±SEM. Differences among groups were tested with the modified Bonferroni test.29 ANOVA with repeated measures was also used to assess the differences in the responses of hemodynamic and metabolic variables to the doses of isoproterenol and CaCl2. A value of P<.05 was considered statistically significant.30


*    Results
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 up arrowMethods
*Results
down arrowDiscussion
down arrowReferences
 
Protocol 1: Effect of L-NAME on the Inotropic Response to ß-Adrenergic Stimulation in the Ischemic Myocardium
An infusion of L-NAME did not affect the coronary hemodynamic parameters under basal conditions (TableDown), indicating that the effects of L-NAME on coronary vascular tone are minimal in the nonischemic myocardium. FS, MO2, LER, and pH of coronary venous blood were not affected by L-NAME administration in the nonischemic condition (Figs 1 to 3). Heart rate increased during infusion of isoproterenol under ischemic conditions, but no significant differences were apparent among the three groups (TableDown). CPP was not altered, as was designed, and CBF was increased after isoproterenol infusion, but no differences were detected among the three groups (TableDown). {Delta}AV(NO) increased in the untreated and L-NAME+L-arginine groups during hypoperfusion and again during administration of isoproterenol but remained unchanged in the L-NAME group (Fig 1Down). Consistent with the decrease in CPP so that CBF was reduced to 60% of the baseline flow, FS, MO2, LER, and pH of coronary venous blood also decreased; the extent of the decrease in LER was significantly greater in the L-NAME group than in the untreated group, and FS in the L-NAME group was smaller than that in the untreated group (Figs 2Down and 3Down). In all of the groups, FS and MO2 increased significantly during intravenous infusion of isoproterenol in a dose-dependent manner; however, FS and MO2 achieved significantly higher values in the L-NAME group than in the other two groups (Fig 2Down). The pH of coronary venous blood and the LER in the L-NAME group were lower than those in the untreated group and the L-NAME+L-arginine group both before and during infusion of isoproterenol (Fig 3Down). Before the reduction in CPP, the Endo/Epi flow ratio was 1.13±0.09 in the untreated group; the ratio decreased to 0.84±0.09 after the reduction in CPP and was not further affected (0.79±0.07) by the administration of isoproterenol 150 ng ·kg-1·min-1. There were no significant differences in the Endo/Epi flow ratio before hypoperfusion and during hypoperfusion in the absence or presence of isoproterenol 150 ng·kg-1·min-1 among the three groups (L-NAME group: baseline, 1.08±0.07; hypoperfusion, 0.81±0.10; isoproterenol, 0.72±0.12. L-NAME+L-arginine group: baseline, 1.16±0.06; hypoperfusion, 0.86±0.04; isoproterenol, 0.83±0.08). There were no significant differences in norepinephrine release (coronary arteriovenous difference in norepinephrinexCBF) among the three groups (untreated group: baseline, 2.65±1.23; hypoperfusion, 1.56±0.98; isoproterenol 150 nmol·kg-1·min-1, 1.71±1.11. L-NAME group: baseline, 2.87±0.89; hypoperfusion, 1.45±0.76; isoproterenol, 1.54±0.98. L-NAME+L-arginine group: baseline, 2.98±1.12; hypoperfusion, 1.39±0.43; isoproterenol, 1.55±0.67 ng·100 g-1·min-1). The augmentation of the isoproterenol-induced inotropic response by L-NAME was not attributable to the attenuation of ischemia, because the pH of coronary venous blood and the LER in the L-NAME group were lower than those in the untreated group (Fig 3Down). These results indicate that endogenous NO released from the ischemic myocardium attenuates the inotropic response to isoproterenol.


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  		Table 1. Sequential Changes in Hemodynamic Parameters



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  		Figure 1. Graph showing coronary arteriovenous difference in nitrate+nitrite concentration [AV(NO)D] before coronary hypoperfusion (control) and after hypoperfusion with and without infusion of isoproterenol in the untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. Values are mean±SEM (n=9). *P<.05, **P<.01 vs untreated group.



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  		Figure 2. Graphs showing effects of myocardial ischemia and isoproterenol on FS (A) and MO2 (B) in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both FS and MO2 were significantly increased (P<.05, multiple ANOVA) by intravenous infusion of isoproterenol. Values are mean±SEM (n=9). *P<.05, **P<.01 vs untreated group.



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  		Figure 3. Graphs showing effects of myocardial ischemia and isoproterenol on pH of coronary venous blood (A) and LER (B) in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both pH and LER were significantly decreased (P<.05, multiple ANOVA) by intravenous infusion of isoproterenol. Values are mean±SEM (n=9). *P<.05, **P<.01 vs untreated group.

Protocol 2: Effect of L-NAME on the CaCl2-Induced Inotropic Response of the Ischemic Myocardium
Infusion of CaCl2 during ischemia increased heart rate, but there were no significant differences among the three groups (TableUp). CPP was not altered, as was designed, and CBF was increased by CaCl2 infusion, but no differences were detected among the groups (TableUp). {Delta}AV(NO) increased in the untreated and L-NAME+L-arginine–treated groups during hypoperfusion and again during infusion of CaCl2 but remained unchanged in the L-NAME group (Fig 4Down). The extent of the decreases in LER and the pH of coronary venous blood in the L-NAME group was greater than those in the untreated group, whereas FS was higher in the L-NAME group than in the untreated group (Figs 5Down and 6Down). The effects of L-NAME on Ca2+-induced inotropic and metabolic responses were blunted by the additional intracoronary infusion of L-arginine. Before the reduction in CPP, the Endo/Epi flow ratio was 1.14±0.08 in the untreated group; the ratio decreased to 0.85±0.09 after the reduction in CPP and was not affected (0.83±0.09) by the administration of CaCl2 3.0 µmol·kg-1·min-1. There were no significant differences in Endo/Epi flow ratio among the three groups (L-NAME group: baseline, 1.11±0.07; CaCl2 1.5 µmol, 0.80±0.08; CaCl2 3.0 µmol, 0.74±0.09. L-NAME+L-arginine group: baseline, 1.23±0.07; CaCl2 1.5 µmol, 0.91±0.05; CaCl2 3.0 µmol, 0.84±0.06). There were no significant differences in norepinephrine release (in ng·100 g-1·min-1) among the three groups (untreated group: baseline, 2.38±1.03; ischemia, 1.80±0.68; CaCl2 3.0 µmol, 1.97±0.76. L-NAME group: baseline, 2.65±0.76; ischemia, 1.64±0.66; CaCl2 3.0 µmol, 1.76±0.87. L-NAME+L-arginine group: baseline, 2.72±1.02; ischemia, 1.45±0.53; CaCl2 3.0 µmol, 1.65±0.87). The augmentation of the Ca2+-induced inotropic response by L-NAME was not attributable to attenuation of ischemia, because the pH of coronary venous blood and LER in the L-NAME group were lower than those in the untreated group (Fig 6Down). These results indicate that endogenous NO released from the ischemic myocardium also attenuates the inotropic response to CaCl2.



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  		Figure 4. Graph showing coronary arteriovenous differences in nitrate+nitrite concentration [AV(NO)D] before coronary hypoperfusion (control) and after hypoperfusion with and without infusion of CaCl2 in the untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. Values are mean±SEM (n=9). *P<.05, **P<.01 vs untreated group.



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  		Figure 5. Graphs showing effects of myocardial ischemia and CaCl2 on FS (A) and MO2 (B) in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both FS and MO2 were significantly increased (P<.05, multiple ANOVA) by intravenous infusion of CaCl2 in a dose-dependent manner. Values are mean±SEM (n=8). *P<.05, **P<.01 vs untreated group.



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  		Figure 6. Graphs showing effects of myocardial ischemia and CaCl2 on pH in coronary venous blood (A) and LER (B) in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both pH and LER were significantly decreased (P<.05, multiple ANOVA) by infusion of CaCl2. Values are mean±SEM (n=9). *P<.05, **P<.01 vs untreated group.

Protocol 3: Effect of L-NAME on the ß-Adrenergic Receptor–Mediated Inotropic Response of the Ischemic Myocardium in Chemically Denervated Hearts
Infusion of L-NAME in the absence or presence of L-arginine had no effect on coronary hemodynamic or metabolic parameters under baseline conditions in any of the three groups with denervated hearts (TableUp). Heart rate increased during infusion of isoproterenol under ischemic conditions, but no significant differences were apparent among the three groups (TableUp). CPP was not altered, as was designed, and CBF was increased after isoproterenol infusion, but no differences were detected among the three groups (TableUp). {Delta}AV(NO) increased in the untreated and L-NAME+L-arginine–treated groups during hypoperfusion and again during isoproterenol administration but remained unchanged in the L-NAME group (Fig 7Down). CPP, FS, MO2, LER, and pH in coronary venous blood also decreased; the extent of the decrease in LER in the L-NAME group was significantly greater than that in the untreated group, whereas FS was significantly higher in the L-NAME group than in the untreated group (Figs 8Down and 9Down). Both FS and MO2 were further increased during infusions of 75 and 150 ng·kg body wt-1·min-1 of isoproterenol compared with the untreated group, in which they were blunted by concomitant infusion of L-arginine (the L-NAME+L-arginine group). pH in the coronary venous blood and LER in the L-NAME group were lower than those in the untreated group and the L-NAME+L-arginine group both before and during infusion of isoproterenol (Fig 9Down). In the untreated group, the Endo/Epi flow ratio was 1.10±0.07 before the reduction in CPP. The Endo/Epi flow ratio decreased to 0.85±0.11 after the reduction in CPP, and it remained unchanged (0.76±0.06) after administration of isoproterenol 150 ng·kg-1·min-1. There were no significant differences in Endo/Epi flow ratio before hypoperfusion or during CPP reduction before and during administration of isoproterenol 150 ng·kg-1·min-1 among the three groups (L-NAME group: baseline, 0.98±0.11; hypoperfusion, 0.72±0.14; isoproterenol, 0.70±0.12. L-NAME+L-arginine group: baseline, 1.13±0.08; hypoperfusion, 0.82±0.10; isoproterenol, 0.78±0.04). The change in norepinephrine release (in ng·100 g-1·min-1) was not observed among the three groups (untreated group: baseline, 0.87±0.53; ischemia, 0.56±0.34; isoproterenol 150 nmol·kg-1·min-1, 0.65±0.31. L-NAME group: baseline, 1.12±0.34; ischemia, 0.65±0.57; isoproterenol, 0.72±0.23. L-NAME+L-arginine group: baseline, 1.01±0.56; ischemia, 0.46±0.33; isoproterenol, 0.53±0.27). These results indicate that endogenous NO released from the ischemic myocardium attenuates myocardial contractility directly, not by inhibiting norepinephrine release.



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  		Figure 7. Graph showing coronary arteriovenous difference in nitrate+nitrite concentration [AV(NO)D] before coronary hypoperfusion (control) and after hypoperfusion in denervated dog with and without infusion of isoproterenol in the untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. Values are mean±SEM (n=5). *P<.05, **P<.01 vs untreated group.



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  		Figure 8. Graphs showing effects of myocardial ischemia and isoproterenol on FS (A) and MO2 (B) in denervated dog in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both FS and MO2 were significantly increased (P<.05, multiple ANOVA) by intravenous infusion of isoproterenol. Values are mean±SEM (n=5). *P<.05, **P<.01 vs untreated group.



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  		Figure 9. Graphs showing effects of myocardial ischemia and isoproterenol on pH of coronary venous blood (A) and LER (B) in untreated ({bullet}), L-NAME ({circ}), and L-NAME+L-arginine ({blacksquare}) groups. In all three groups, both pH and LER were significantly decreased (P<.05, multiple ANOVA) by intravenous infusion of isoproterenol. Values are mean±SEM (n=5). *P<.05, **P<.01 vs untreated group.


*    Discussion
up arrowTop
 up arrowAbstract
 up arrowIntroduction
 up arrowMethods
up arrowResults
*Discussion
down arrowReferences
 
We have shown that L-NAME, which inhibits endogenous NO production, enhances the inotropic responses to isoproterenol and CaCl2 in the ischemic myocardium, which are restored by L-arginine. L-NAME increased anaerobic myocardial metabolism, which was also reversed by L-arginine. These results suggest that endogenous NO released from the ischemic myocardium attenuates positive inotropic responses and thereby inhibits the progression of anaerobic myocardial metabolism.

Cellular Mechanism by Which NO Affects Myocardial Contractility
Several possible mechanisms may account for the effect of L-NAME on myocardial contractility during ischemia: (1) L-NAME per se may have a positive inotropic effect. However, this possibility is not likely, given that FS was not affected by this compound under nonischemic conditions. (2) Inhibition of NO production by L-NAME decreases the degree of ischemia. If the steal phenomenon of coronary flow from the ischemic area to the nonischemic area or from endocardium to epicardium in the ischemic area is attenuated by L-NAME, then the drug may reduce the extent of ischemia by improving myocardial perfusion, resulting in the observed increase in myocardial contractility. However, this possibility is also unlikely, because administration of L-NAME did not affect the myocardial Endo/Epi flow ratio and resulted in a decrease in both LER and pH in coronary venous blood. These results indicate that L-NAME did not alter myocardial perfusion and improved myocardial ischemia in the present study. (3) Given that NO inhibits norepinephrine release from sympathetic nerve endings,31 L-NAME may enhance the release of norepinephrine and thereby increase contractile function. However, in the present study, L-NAME did not affect norepinephrine release from the ischemic myocardium. Furthermore, the increased inotropic response to isoproterenol in the L-NAME group was also observed in chemically denervated hearts. Thus, the contribution of an increase in norepinephrine release from sympathetic nerve endings may be minimal. (4) NO inhibits platelet aggregation32 33 34 35 and neutrophil adherence to the coronary vasculature,36 37 which may enhance myocardial anaerobic metabolism. On this basis, myocardial contractility should be decreased in the L-NAME group as a result of progressive aggregation of platelets and adherence of neutrophils. However, increased platelet aggregation and leukocyte adherence attributable to L-NAME appear unlikely because we observed an increase in myocardial contractility with worsening myocardial ischemia. (5) L-NAME has been shown to modulate cholinergic effects in addition to the inhibition of NO synthase,38 which may affect myocardial contractility in ischemic myocardium. Buxton et al38 reported that the antagonistic effects of muscarinic receptors by L-NAME are not blunted by L-arginine; however, the increases in the inotropic response of ischemic myocardium due to L-NAME was blunted by L-arginine in the present study, suggesting that NO may be responsible for the inotropic effect of L-NAME observed in the present study. Thus, we conclude that NO decreases myocardial contractility in ischemic myocardium by its direct action.

Although we observed that myocardial inotropic effects of isoproterenol and CaCl2 are enhanced by the L-NAME, Balligand et al5 reported the selective effects of NO on ß-adrenergic stimulation. This difference between the Balligand et al and the present studies may be attributable to the differences in the species and models of the experiments (rat cardiomyocyte versus canine hearts) and the differences in the conditions of the heart (normoxic versus ischemic conditions).

Increases in cellular cGMP concentration decrease myofilament sensitivity to Ca2+ in intact cardiac myocytes6 and may also modify the intracellular Ca2+ concentration, suggesting that cGMP plays a role in modulating myocardial contraction. Biochemical and pharmacological studies with ventricular myocytes have shown that the negative inotropic action of NO is mediated by cGMP accumulation.39 In the adult myocardium, an increase in cGMP inhibits Ca2+ influx and reduces the positive inotropic effect of an increase in cAMP induced by ß-adrenergic receptor stimulation,5 consistent with the results of the present study. Alternatively, the effect of NO inhibition may change myocardial contractility through alteration of heart rate. The inotropic effect of NO synthase inhibition has been reported to be related to the stimulation frequency through the modulation of ion channels in isolated papillary muscle preparations.40 However, this mechanism is not likely, because heart rate did not change with and without L-NAME administration in the ischemic heart (TableUp).

Our study provides functional and biochemical evidence for the generation of NO by an isoform of NOS that appears to be constitutively present in canine myocardium. Although NOS is induced in rat vascular smooth muscle cells by interleukin-1ß,41 it is unlikely that myocardial NOS is induced by cytokines in the present study, because the NO-mediated response to ischemia in the present study is rapid.

Pathophysiological Relevance
The question arises as to whether the increase in myocardial contractility induced by L-NAME is beneficial or deleterious to the ischemic heart. Our study suggests that L-NAME treatment is deleterious, because we observed that the LER and the pH of coronary venous blood during infusion of isoproterenol were lower in the L-NAME–treated group than in the untreated group, indicating that anaerobic myocardial metabolism in the ischemic heart is increased by L-NAME treatment. The ischemic myocardium thus appears to be forced to contract at the expense of a further increase in myocardial anaerobic metabolism.

Furthermore, there is a possibility that endogenous NO directly affects the anaerobic metabolism of ischemic myocardium. Ljusegren et al42 suggested that cGMP reduces lactate accumulation in the hypoxic, nonbeating ventricular muscle: Not only increased blood supply but also diminished lactate production due to NO and cGMP may be responsible for the attenuation of myocardial ischemia. Furthermore, Beitner et al43 reported that cGMP inhibits phosphofructokinase of cardiac and skeletal muscles and suggested that the inhibition of activity of phosphofructokinase may decrease the whole glycogenolysis and glycolysis. These actions of cGMP in ischemic myocardium may contribute to the NO-dependent inhibition of anaerobic metabolism.

The administration of NOS inhibitors to anesthetized or conscious animals has been shown to induce cardiac depression as well as systemic hypertension and marked systemic vasoconstriction,44 45 which appears to contradict the present observations. Various mechanisms may underlie this apparent discrepancy. Hypertension induced by NOS inhibitor may stimulate a baroreceptor reflex and a consequent reduction in cardiac output. Increased afterload may also result in a decrease in ventricular stroke volume. These systemic hemodynamic effects of NOS inhibitors may reduce cardiac output. Furthermore, NOS inhibitors induce coronary vasoconstriction and thereby reduce myocardial oxygen supply.46 47 In our experimental model, coronary perfusion pressure was maintained constant during hypoperfusion, and because L-NAME was selectively infused into the LAD, it did not affect systemic blood pressure or afterload. Thus, our results might have differed if we had administered L-NAME systemically.

Recently, Weyrich et al48 showed that physiologically relevant concentrations of NO did not induce physiologically significant negative inotropic effects acutely; NO exerted a statistically significant negative inotropic effect only in the presence of high concentrations of norepinephrine. In our study, FS, MO2, LER, and pH of coronary venous blood were not affected by L-NAME or L-arginine administration under nonischemic conditions, which may correspond to the control conditions of Weyrich et al.48 An increase in vagal nerve activity reduces the contractile response to sympathetic stimulation49 and infused ß-adrenergic agonists.50 51 52 Studies have also shown that NO53 and NO donors54 reduce myocardial contraction in an in vivo model. We have also shown that NO modulates myocardial contractility, suggesting that increased release of NO during ischemia reduces myocardial contractility or that the ischemic myocardium is more sensitive to NO.

Clinical Relevance
In the clinical setting, myocardial ischemia is often followed by reperfusion with percutaneous transluminal coronary revascularization and percutaneous transluminal coronary angioplasty. Hasebe et al55 showed that endogenous NO attenuates myocardial stunning in dogs. Furthermore, exogenous NO precursors56 and angiotensin-converting enzyme inhibitors57 58 reduce the infarct size, with attenuation of myocardial ischemia and reperfusion.59 The present findings suggest that the beneficial effects of NO donors or angiotensin-converting enzyme inhibitors are partially attributable to a reduction in the extent of myocardial ischemia because of a myocardial energy-sparing effect as well as coronary vasodilation. Beckman and colleagues60 proposed that NO combined with superoxide can yield the peroxide anion (ONOO-) and that this anion decomposes into the highly reactive hydroxyl radical. These free radicals may be involved in myocardial cellular injury. During reperfusion after sustained ischemia, NO may have bidirectional effects on myocardium because of the coexistence of NO and O2-. Because we used the hypoperfusion model, ONOO- may not have contributed to our results. Further investigation is required to determine whether endogenous NO participates in a negative feedback system to enhance the contractility induced by ß-adrenergic receptor stimulation and exerts a protective effect in ischemia-reperfusion models before the present observations can be applied to the clinical setting.


*    Selected Abbreviations and Acronyms
 
{Delta}AVO2 = arteriovenous blood oxygen difference
CBF = coronary blood flow
CPP = coronary perfusion pressure
Endo/Epi = endocardial-to-epicardial (ratio)
FS = fractional shortening
L-NAME = NG-nitro-L-arginine methyl ester
LAD = left anterior descending coronary artery
LER = lactate extraction ratio
MO2 = myocardial oxygen consumption
NO = nitric oxide
NOS = NO synthase


*    Acknowledgments
 
We thank Noriko Tamai and Shinya Suzuki for their technical assistance.

Received May 23, 1995; revision received July 26, 1995; accepted August 29, 1995.


*    References
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*References
 

  1. Furchgott RF, Zawadzki JV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature. 1980;288:373-376. [Medline] [Order article via Infotrieve]
  2. Palmer RMJ, Ferrige AG, Moncada S. Nitric oxide release accounts for the biological activity of endothelium-derived relaxing factor. Nature. 1987;327:524-527. [Medline] [Order article via Infotrieve]
  3. Shah AM, Lewis MJ. Modulation of myocardial contraction by endocardial and coronary vascular endothelium. Trends Cardiovasc Med. 1993;3:98-103.
  4. Ramacioti C, Sharkey A, McClellan G, Winegrad S. Endothelial cells regulate cardiac contractility. Proc Natl Acad Sci U S A. 1992;89:33-36. [Abstract/Free Full Text]
  5. Balligand JL, Kelly RA, Marsden PA, Smith TW, Michel T. Control of cardiac muscle cell function by an endogenous nitric oxide signaling system. Proc Natl Acad Sci U S A. 1993;90:347-351. [Abstract/Free Full Text]
  6. Shah AM, Spurgeon H, Sollot SJ, Talo A, Lakatta EG. 8-Bromo cGMP reduces the myofilament response to Ca2+ in intact cardiac myocytes. Circ Res. 1994;74:970-978. [Abstract/Free Full Text]
  7. Nawrath H. Does cyclic GMP mediate the negative inotropic effect of acetylcholine in the heart? Nature. 1977;267:72-74. [Medline] [Order article via Infotrieve]
  8. Brady AJB, Poole-Wilson PA, Harding SE, Warren JB. Nitric oxide production within cardiac myocytes reduces their contractility in endotoxemia. Am J Physiol. 1992;263:H1963-H1966. [Abstract/Free Full Text]
  9. Brady AJB, Warren JB, Poole-Wilson PA, Williams TJ, Harding SE. Nitric oxide attenuates cardiac myocyte contraction. Am J Physiol. 1993;265:H176-H186. [Abstract/Free Full Text]
  10. Suffredini AF, Fromm RE, Parker MM. The cardiovascular response of normal humans to the administration of endotoxin. N Engl J Med. 1989;321:2807-2810.
  11. Sobotka PA, McMannis J, Fisher RI, Stein DG, Thomas J. Effects of interleukin 2 on cardiac function in the isolated rat heart. J Clin Invest. 1990;86:845-850.
  12. Finkel MS, Oddis CV, Jacob TD, Watkins SC, Hattler BG, Simmons RL. Negative inotropic effects of cytokines on the heart mediated by nitric oxide. Science. 1992;257:387-389. [Abstract/Free Full Text]
  13. Shah AM, Evans HG, Lewis MJ. Interleukin-1ß mimics the characteristic effect of endothelium-derived relaxing factor (EDRF) on myocardial contraction. J Vasc Res. 1992;29:195-198.
  14. Knowles RG, Salter M, Brooks SL, Moncada S. Anti-inflammatory glucocorticoids inhibit the induction of nitric oxide synthase by endotoxin in the rat. Biochem J. 1990;270:833-836. [Medline] [Order article via Infotrieve]
  15. Kitakaze M, Node K, Komamura K, Minamino T, Inoue M, Hori M, Kamada T. Evidence for nitric oxide generation in cardiomyocytes: its augmentation by hypoxia. J Mol Cell Cardiol. 1995;27:2149-2154. [Medline] [Order article via Infotrieve]
  16. Node K, Kitakaze M, Kosaka H, Komamura K, Minamino T, Tada M, Inoue M, Hori M, Kamada T. Plasma nitric oxide end products are increased in the ischemic canine heart. Biochem Biophys Res Commun. 1995;211:370-374. [Medline] [Order article via Infotrieve]
  17. Balligand JL, Ungureanu D, Kell RA, Kobzik L, Pimental D, Michel T, Smith TW. Abnormal contractile function due to induction of nitric oxide synthesis in rat cardiac myocytes follows exposure to activated macrophage-conditioned medium. J Clin Invest. 1993;91:2314-2319.
  18. Miloslav M, Schrader J. Role of nitric oxide in reactive hyperemia of the guinea pig heart. Circ Res. 1992;70:208-212. [Abstract/Free Full Text]
  19. Park HA, Rubin LE, Gross RS, Levi R. Nitric oxide is a mediator of hypoxic coronary vasodilatation. Circ Res. 1992;71:992-1001. [Abstract/Free Full Text]
  20. Zweier JL, Wang P, Kuppusamy P. Direct measurement of nitric oxide generation in the ischemic heart using electron paramagnetic resonance spectroscopy. J Biol Chem. 1995;270:304-307. [Abstract/Free Full Text]
  21. Kitakaze M, Hori M, Gotoh K, Sato H, Iwakura K, Kitabatake A, Inoue M, Kamad T. Beneficial effects of {alpha}2-adrenoceptor activity on ischemic myocardium during coronary hypoperfusion in dogs. Circ Res. 1989;65:1632-1645. [Abstract/Free Full Text]
  22. Mori H, Haruyama S, Shinozaki Y, Okino H, Iida A, Takanashi R, Sakura I, Husseini W, Payne B, Hoffman JIE. New nonradioactive microspheres and more sensitive x-ray fluorescence to measure regional blood flow. Am J Physiol. 1992;263:H1946-H1957. [Abstract/Free Full Text]
  23. Archie JP, Fixler DE, Ulyot DJ, Hoffman JIE, Utler JR, Carlson EL. Measurement of cardiac output with an organ trapping of radioactive microspheres. J Appl Physiol. 1973;35:148-154. [Free Full Text]
  24. Green LC, Tannenbaum SR, Goldman P. Nitrate synthesis in the germfree and conventional rat. Science. 1991;212:56-58.
  25. Green LC, Wagner DA, Glogowski J, Skipper PL, Wishnok JS, Tannenbaum SR. Analysis of nitrate, nitrite and [15N]nitrate in biological fluids. Anal Biochem. 1982;126:131-138. [Medline] [Order article via Infotrieve]
  26. Kosaka H, Tsuda M, Kurashima Y, Esumi H, Terada N, Ito Y, Uozumi M. Marked nitration by stimulation with lipopolysaccharide in ascorbic acid-deficient rats. Carcinogenesis. 1990;11:1887-1889.[Abstract/Free Full Text]
  27. Kosaka H, Sakaguchi H, Sawai Y, Kumura E, Seiyama A, Sheng-Song C, Shiga T. Effect of interferon-{gamma} on nitric oxide and hemoglobin production in endotoxin-treated rats and its synergism with interleukin 1 or tumor necrosis factor. Life Sci. 1994;54:1523-1529. [Medline] [Order article via Infotrieve]
  28. Sato H, Inoue M, Matsuyama T, Ozaki H, Shimazu T, Takeda H, Ishida Y, Kamada T. Hemodynamic effects of the ß1-adrenoceptor partial agonist xamoterol in relation to plasma norepinephrine levels during exercise in patients with left ventricular dysfunction. Circulation. 1989;75:213-220. [Abstract/Free Full Text]
  29. Winer BJ. Statistical Principles in Experimental Design. 2nd ed. New York, NY: Mcgraw-Hill; 1982.
  30. Snedecor GW, Cochran WG. Statistical Methods. 6th ed. Ames, Iowa: Iowa State University Press; 1972:258-298.
  31. Sakuma I, Togashi H, Yasuda H, Gross S, Levi R. NG-Methyl-L-arginine, an inhibitor of L-arginine–derived nitric oxide synthesis, stimulates renal sympathetic nerve activity in vivo: a role for nitric oxide in the central regulation of sympathetic tone? Circ Res. 1992;70:607-611. [Abstract/Free Full Text]
  32. Sneddon JM, Vane JR. Endothelium-derived relaxing factor reduces platelet adhesion to bovine endothelial cells. Proc Natl Acad Sci U S A. 1988;85:2800-2804. [Abstract/Free Full Text]
  33. Mollace V, Salnemini D, Anggard E, Vane J. Nitric oxide from vascular smooth muscle cells: regulation of platelet reactivity and smooth muscle cell guanylate cyclase. Br J Pharmacol. 1991;104:633-638. [Medline] [Order article via Infotrieve]
  34. Graaf JC, Banga JD, Moncada S, Palmer RMJ, Groot PG, Sixma JJ. Nitric oxide functions as an inhibitor of platelet adhesion under flow conditions. Circulation. 1992;85:2284-2290. [Abstract/Free Full Text]
  35. Komamura K, Node K, Kosaka H, Inoue M. Endogenous nitric oxide inhibits microthromboembolism in the ischemic heart. Circulation. 1994;90(suppl I):I-345. Abstract.
  36. Ma XL, Weyrich AS, Lefer DJ, Lefer AM. Diminished basal nitric oxide release after myocardial ischemia and reperfusion promotes neutrophil adherence to coronary endothelium. Circ Res. 1993;72:403-412. [Abstract/Free Full Text]
  37. Wright CD, Mulsch A, Busse R, Osswald H. Generation of nitric oxide by human neutrophils. Biochem Biophys Res Commun. 1989;160:813-819. [Medline] [Order article via Infotrieve]
  38. Buxton ILO, Cheek BD, Eckman D, Westfall DP, Sanders KM, Keef KD. NG-Nitro L-arginine methyl ester and other alkyl esters of arginine are muscarinic receptor antagonists. Circ Res. 1993;72:387-395. [Abstract/Free Full Text]
  39. Mery PF, Pavoine C, Belhassen L, Pecker F, Fischmeister R. Nitric oxide regulates cardiac Ca2+ current: involvement of cGMP-inhibited and cGMP-stimulated phosphodiesterases through guanylyl cyclase activation. J Biol Chem. 1993;268:26286-26295. [Abstract/Free Full Text]
  40. Finkel MS, Oddis CV, Mayer H, Hattler BG, Simmons RL. Nitric oxide synthase inhibitor alters papillary muscle force-frequency relationship. J Pharmacol Exp Ther. 1995;272:942-952.
  41. Konno Y, Hirata K, Imai T, Marumo F. Induction of nitric oxide synthase gene by interleukin in vascular smooth muscle cells. Hypertension. 1993;22:34-39. [Abstract/Free Full Text]
  42. Ljusegren ME, Axelsson KL. Lactate accumulation in isolated hypoxic rat ventricular myocardium: effect of different modulators of the cyclic GMP system. Pharmacol Toxicol. 1993;72:56-60. [Medline] [Order article via Infotrieve]
  43. Beitner R, Haberman S, Cycowitz T. The effect of cyclic GMP on phosphofructokinase from rat tissues. Biochim Biophys Acta. 1977;482:330-340. [Medline] [Order article via Infotrieve]
  44. Elsner D, Muntze A, Kromer EP, Riegger GAJ. Systemic vasoconstriction induced by inhibition of nitric oxide synthesis is attenuated in conscious dogs with heart failure. Cardiovasc Res. 1991;25:438-440. [Medline] [Order article via Infotrieve]
  45. Gardiner SM, Compton AM, Kemp PA, Bennett T. Regional and cardiac haemodynamic effects of NG-nitro-L-arginine methyl ester in conscious, Long Evans rats. Br J Pharmacol. 1990;101:625-631. [Medline] [Order article via Infotrieve]
  46. Kelm M, Schrader J. Control of coronary vascular tone by nitric oxide. Circ Res. 1990;66:1561-1575. [Abstract/Free Full Text]
  47. Ueeda M, Silvia SK, Olsson RA. Nitric oxide modulates coronary autoregulation in the guinea pig. Circ Res. 1992;70:1296-1303. [Abstract/Free Full Text]
  48. Weyrich AS, Ma XL, Buerke M, Murohara T, Armstead VE, Lefer AM, Nicolas JM, Thomas AP, Lefer DJ, Johansen JV. Physiological concentrations of nitric oxide do not elicit an acute negative inotropic effect in unstimulated cardiac muscle. Circ Res. 1994;75:692-700. [Abstract/Free Full Text]
  49. Henning RJ, Khalil IR, Levy MN. Vagal stimulation attenuates sympathetic enhancement of left ventricular function. Am J Physiol. 1990;258:H1470-H1475. [Abstract/Free Full Text]
  50. Vatner SF, Rutherford JS, Ochs HR. Baroreflex and vagal mechanisms modulating left ventricular contractile responses to sympathetic amines in conscious dogs. Circ Res. 1979;44:195-207. [Free Full Text]
  51. Fujii AM, Vatner SF. Autonomic mechanisms regulating myocardial contractility in conscious animals. Pharmacol Ther. 1985;29:221-238. [Medline] [Order article via Infotrieve]
  52. Landzberg JS, Parker JD, Gauthier DF, Colucci WS. Effects of intracoronary acetylcholine and atropine on basal and dobutamine-stimulated left ventricular contractility. Circulation. 1994;89:164-168. [Abstract/Free Full Text]
  53. Paulus WJ, Vantrimpont PJ, Shah AM. Acute effects of nitric oxide on left ventricular relaxation and diastolic distensibility in humans: assessment by bicoronary sodium nitroprusside infusion. Circulation. 1994;89:2070-2078. [Abstract/Free Full Text]
  54. Hare JM, Keaney JF, Balligand JL, Loscalzo J, Smith TW. Role of nitric oxide in parasympathetic modulation of ß-adrenergic myocardial contractility in normal dogs. J Clin Invest. 1995;95:360-366.
  55. Hasebe N, Shen YT, Vatner SF. Inhibition of endothelium-derived relaxing factor enhances myocardial stunning in conscious dogs. Circulation. 1993;64:1101-1107. [Abstract/Free Full Text]
  56. Lefer DJ, Nakanishi K, Johnston WE, Vinten-Johansen J. Antineutrophil and myocardial protecting action of a novel nitric oxide donor after acute myocardial ischemia and reperfusion in dogs. Circulation. 1993;88:2337-2350. [Abstract/Free Full Text]
  57. Linz W, Martorana PA, Scholkens BA. Local inhibition of bradykinin degradation in ischemic hearts. J Cardiovasc Pharmacol. 1990;15:S99-S109.
  58. Martorana PA, Kettenbach B, Breipohl H, Linz W, Scholkens BA. Reduction of infarct size by local angiotensin-converting enzyme inhibition is abolished by a bradykinin antagonist. Eur J Pharmacol. 1990;182:395-396. [Medline] [Order article via Infotrieve]
  59. Kitakaze M, Minamino T, Node K, Komamura K, Shinozaki Y, Mori H, Kosaka H, Inoue M, Hori M, Kamada T. Beneficial effects of inhibition of angiotensin-converting enzyme on ischemic myocardium during coronary hypoperfusion in dogs. Circulation. 1995;92:950-961. [Abstract/Free Full Text]
  60. Beckman JS, Beckman TW, Chen J, Marshall PA, Freeman BA. Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide. Proc Natl Acad Sci U S A. 1990;87:1620-1624.[Abstract/Free Full Text]



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