From the Abteilung für Pathophysiologie, Zentrum für Innere
Medizin des Universitätsklinikums Essen, Germany.
Correspondence to Prof Dr Gerd Heusch, FESC, FACC, Abteilung für Pathophysiologie, Zentrum für Innere Medizin, Universitätsklinikum Essen, Hufelandstraße 55, 45122 Essen, Federal Republic of Germany.
Methods and Results—In 71 enflurane-anesthetized swine,
severe left anterior descending coronary artery hypoperfusion
for 90 minutes followed by 2 hours of reperfusion resulted in an
infarct size (IS, by triphenyltetrazolium
chloride) of 16.7±3.4% (SEM) of the area at risk. IPc by 2 minutes of
low-flow ischemia and 15 minutes of reperfusion before the
90-minute target ischemia did not reduce IS (21.9±7.0%). IS
was decreased to 9.0±2.6% (P<0.05) by 3 minutes of
IPc and reduced further to 1.9±0.9% (P<0.05) by 10
minutes of IPc. The interstitial adenosine
concentration (microdialysis, high-performance liquid
chromatography) was unchanged with 2 and 3 minutes of
IPc but increased with 10 minutes of IPc (by 573±144%). The
interstitial bradykinin concentration (microdialysis,
radioimmunoassay) remained unchanged with 2 minutes of IPc but
increased to a similar extent with 3 minutes (by 198±32%) and 10
minutes (by 224±30%) of IPc. The IS reduction by 3 minutes of IPc was
abolished by blockade of the bradykinin B2 receptor with
intracoronary HOE 140 (16.6±4.3%) but not with
intracoronary infusion of adenosine deaminase
(8.4±2.5%, P<0.05). HOE 140, however, did not affect
the IS reduction (3.5±1.1%, P<0.05) by 10 minutes of
IPc. Combined infusion of HOE 140 and adenosine deaminase
abolished the IS reduction by 10 minutes of IPc (15.4±6.7%).
Conclusions—IS reduction by IPc is a graded phenomenon. Whereas
bradykinin is essential during preconditioning ischemia of
shorter duration, adenosine is more important during
preconditioning ischemia of longer duration.
It remains unclear, however, whether ischemic
preconditioning, above a certain threshold, is an all-or-nothing or a
graded phenomenon.6 8 9 10 11 In anesthetized
rabbits, infarct size was not significantly reduced further by 2
episodes10 or 4 episodes6 of 5 minutes of
ischemia and 10 minutes of reperfusion over that by a single
preconditioning episode of 5 minutes of ischemia and 10 minutes
of reperfusion, whereas in another study, infarct size was
significantly decreased further with 3 preconditioning cycles of 5
minutes of ischemia and 10 minutes of reperfusion over that by
a single preconditioning cycle.11 Similarly, data
in anesthetized pigs suggested, although it was not proven
statistically, that infarct size reduction by ischemic
preconditioning is a graded rather than an all-or-nothing
phenomenon.9
We now tested in enflurane-anesthetized swine whether
infarct size reduction by ischemic preconditioning depends on
the strength of the preconditioning stimulus, and we therefore varied
the duration of the preconditioning ischemia (3 minutes versus
10 minutes). In swine, the importance of adenosine and
activation of ATP-dependent potassium channels for ischemic
preconditioning has been documented4,12; the
contribution of bradykinin to ischemic preconditioning in swine
has not been determined thus far. We therefore measured the
interstitial adenosine and bradykinin
concentrations by microdialysis. In a second step, we used
adenosine deaminase and a bradykinin
B2–receptor antagonist to eliminate
the contribution of either adenosine or bradykinin to
preconditioning by 3 minutes versus 10 minutes of ischemia and
15 minutes of reperfusion preceding a sustained 90-minute index
ischemia.
Experimental Model
Regional Myocardial Blood Flow
Interstitial Adenosine and Bradykinin
Adenosine Deaminase
Blockade of the Bradykinin B2 Receptor
Morphology
Experimental Protocols
In all swine, a 90-minute sustained index ischemia was followed
by 120 minutes of reperfusion to facilitate the identification of
necrotic tissue. During ischemia, blood flow to the LAD was
reduced to a level sufficient to reduce the regional work index by
Protocol A: Infarct Size Reduction by Preconditioning
Ischemia of Different Durations
IPc2 Group (n=5)
IPc3 Group (n=7)
IPc10 Group (n=7)
Protocol B: Contribution of Adenosine and Bradykinin to
Infarct Size Reduction
HOE-Control Group (n=8)
HOE-IPc3 Group (n=9)
HOE-IPc10 Group (n=8)
HOE-Dea-Control Group (n=7)
HOE-Dea-IPc10 Group (n=6)
Data Analysis and Statistics
Statistical analysis was performed with SYSTAT software.
Hemodynamic and biochemical data were compared by 2-way
ANOVA for repeated measures. Area at risk and infarct size were
compared by 1-way ANOVA. When significant differences were detected,
individual mean values were compared by post hoc tests. All data are
reported as mean±SEM, and a value of P<0.05 was accepted
as indicating a significant difference in mean values. Linear
regression analyses between subendocardial blood flow at 5
minutes of ischemia and infarct size were performed in all
groups. Regression lines were compared by ANCOVA.
Protocol A: Infarct Size Reduction by Preconditioning
Ischemia of Different Durations
Interstitial Adenosine and Bradykinin
Myocardial Infarction
Protocol B: Contribution of Adenosine and Bradykinin to
Infarct Size Reduction
Interstitial Adenosine and Bradykinin
Myocardial Infarction
Hypoperfusion at low flow made it possible that adenosine
deaminase and HOE 140 could be administered throughout the
ischemic period, ensuring a homogeneous delivery at
a high concentration but without effects on systemic
hemodynamics. Also, infarct development could be
related to ischemic subendocardial blood flow, and thus, a more
sensitive end point than infarct size per se could be used, because
even in collateral-deficient species, some flow variations during total
coronary artery occlusion occur.17
With microdialysis, absolute concentrations of substances within the
interstitial space cannot be determined, because complete
equilibration between the buffer within the dialysate membrane and the
interstitial fluid does not occur at perfusion rates of 0.5
to 5.0 µL/min.18 Furthermore, the exchange rate
of the microdialysis membrane in vivo might be different from the
exchange rate determined in vitro. Therefore, the adenosine and
bradykinin concentrations in the present study cannot be taken in
exactly quantitative terms but rather qualitatively reflect the
involvement of these triggers in ischemic preconditioning.
Ischemic Preconditioning: A Graded Phenomenon
Controversy remains as to whether or not, above such threshold,
ischemic preconditioning is a graded or an all-or-nothing
phenomenon. In anesthetized dogs8 and
rabbits,6 10 the infarct size reduction by 1
single episode of 5 minutes of ischemia with 10 minutes of
reperfusion was as effective as preconditioning with
2,10 4,6 or
128 such episodes of preconditioning
ischemia/reperfusion. In contrast, in anesthetized
swine, 1 single episode of 10 minutes of ischemia and 30
minutes of reperfusion reduced infarct size from 71.3±4.4% to
54.3±10.2% (P=NS), but infarct size was further reduced
when 2 such preconditioning episodes were used (25.6±3.9%,
P<0.05).9 The level of significance
for protection with 1 single preconditioning episode was possibly
missed only because of the small number of animals studied. Similarly,
in a recent study in anesthetized rabbits, 1 single episode of
5 minutes of ischemia with 10 minutes of reperfusion reduced
infarct size compared with placebo (36% versus 60%) but to a much
lesser extent than 3 such episodes (0.6%).11
The previous studies varied the number of preconditioning
cycles of constant duration to vary the intensity of the
preconditioning stimulus, whereas in the present study, the
duration of a single preconditioning ischemic episode was
varied; therefore, results are not necessarily transferable.
Sources of Adenosine and Bradykinin
The cellular origin of bradykinin during ischemia is
unclear. The reduction in oxygen supply is unlikely to cause the
release or production of bradykinin, especially because the
endothelium is more resistant to
ischemia/reperfusion injury than the cardiomyocyte
itself.24 With the reduction in flow, however,
the mechanical forces on the endothelium are altered.
Experimental data for the dependence of bradykinin
release/production on mechanical forces, however, are lacking.
Altered proton release during flow restriction could also increase the
bradykinin concentration, because a reduction in plasma pH can
activate plasma kallikrein and reduce kinin
breakdown.25 Indeed, coronary venous pH,
as a gross measure of proton production, was lower during the
initial preconditioning ischemic period in the IPc3 group (from
7.392±0.015 under control conditions to 7.347±0.017 with 3 minutes of
ischemia, P<0.05) and the IPc10 group (from
7.352±0.017 to 7.204±0.025 with 10 minutes of ischemia,
P<0.05) than in the IPc2 group (from 7.391±0.025 to
7.371±0.028 with 2 minutes of ischemia, P=NS), and
only in the IPc3 and IPc10 groups was an increased
interstitial bradykinin concentration measured during the
preconditioning cycle of ischemia/reperfusion. Although the
source/trigger of bradykinin release/production remains
unclear, in a previous study in anesthetized dogs, increased
coronary venous bradykinin concentration was measured as early
as after 3 to 5 minutes of
ischemia.26
Contribution of Adenosine and Bradykinin to Ischemic
Preconditioning
In conclusion, infarct size reduction by a single episode of
preconditioning ischemia/reperfusion is a graded rather than an
all-or-nothing phenomenon in the anesthetized swine in situ.
Although bradykinin is essential during preconditioning
ischemia of shorter duration, adenosine is more
important during preconditioning ischemia of longer
duration.
Received February 16, 1998;
revision received March 24, 1998;
accepted April 21, 1998.
© 1998 American Heart Association, Inc.
Basic Science Reports
Ischemic Preconditioning in Pigs: A Graded Phenomenon
Its Relation to Adenosine and Bradykinin
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—A threshold concept for
ischemic preconditioning (IPc) has been proposed. It is
unclear, however, whether IPc, above a certain threshold, is an
all-or-nothing or a graded phenomenon.
Key Words: ischemia • adenosine • bradykinin
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
The delay of
infarct size development by ischemic preconditioning is the
most powerful endogenous cardioprotective phenomenon
determined thus far.1 Endogenous
activation of adenosine receptors in
rabbits,2 dogs,3 and
swine,4 
1-adrenergic
receptor in dogs,5 bradykinin
B2 receptors in rabbits,6
and opioid receptors in rats7 have been shown to
be involved in the infarct size reduction achieved by ischemic
preconditioning. In anesthetized rabbits, blockade of the
bradykinin B2 receptor abolished the infarct size
reduction by ischemic preconditioning with 1 cycle of 5 minutes
of ischemia and 5 minutes of reperfusion preceding 30 minutes
of sustained index ischemia.6 However,
with 4 such cycles of preconditioning ischemia/reperfusion,
blockade of the bradykinin B2 receptor no longer
abolished the infarct size reduction by ischemic
preconditioning.6 From these data, Downey and
coworkers derived a threshold concept of ischemic
preconditioning, in that a certain number of triggers during the
preconditioning ischemia/reperfusion are necessary to achieve
an infarct size reduction.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
The experimental protocols used in this study were approved by
the Bioethical Committee of the district of Düsseldorf, and they
adhere to the guiding principles of the American Physiological
Society.
The experimental model has been described extensively in a
previous publication4; in brief, in 71
enflurane-anesthetized Göttinger miniswine (20 to 40 kg),
a micromanometer was placed in the left ventricle
through the apex. Ultrasonic dimension gauges were implanted in the
left ventricular myocardium to measure the
thickness of the anterior and posterior (control) walls. The proximal
left anterior descending coronary artery (LAD) was cannulated
and perfused from an extracorporeal circuit. Left atrial pacing was
performed at 10 bpm above sinus rhythm to avoid baroreflex-mediated
changes in heart rate.
Radiolabeled microspheres (15 µm in diameter;
141Ce, 114In,
51Cr, 113Sn,
103Ru, 95Nb, or
46Sc; NEN-DuPont Co) were injected into the
coronary perfusion circuit to determine the regional myocardial
blood flow and its distribution throughout the LAD perfusion bed (model
5912, Gammaszint BF 5300 Packard).13
Microdialysis probes (CMA/220, Bioanalytical Systems, Inc)
were inserted into the LAD perfusion bed.4 Except
for the first ischemia/reperfusion period, in which the
effluent was collected over 2 or 3 or 10 and 15 minutes, respectively,
all other dialysates were collected in 10-minute fractions. For the
analysis of interstitial adenosine, a
15-µL aliquot of the microdialysis sample was subjected to
high-performance liquid
chromatography.4 The
interstitial bradykinin was measured with a commercially
available kit (Peninsula Laboratories Inc).
The dose of adenosine deaminase (5 IU · mL
blood-1 · min-1)
attenuated the cardioprotection achieved by ischemic
preconditioning with 10 minutes of ischemia and 15 minutes of
reperfusion in a previous study.4
In 4 separate dose-finding experiments, intracoronary
infusion of bradykinin increased coronary inflow in a
dose-dependent manner and, at a concentration of 70 nmol/L, by more
than 2-fold. The concentration of HOE 140 that nearly completely
blocked this increase in blood flow was 0.01 µg ·
kg-1 · min-1
IC.
At the end of each study, the heart was removed and sectioned
from base to apex into 5 transverse slices in a plane parallel to the
atrioventricular groove. The slices were immersed in a
0.09-mol/L sodium phosphate buffer (pH 7.4) containing 1.0% triphenyl
tetrazolium chloride (Sigma) and 8% dextran (MW 77 800) for 20
minutes at 37°C to identify infarcted tissue. The amount of infarcted
tissue is expressed as a percentage of the left ventricular
area at risk as determined by the microsphere
technique.4
A scheme of the protocols is presented in Figure 1
.
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Figure 1. Schematic of the 10 different
protocols 
90%. During steady-state ischemia, microspheres
were injected into the LAD perfusion bed, and systemic
hemodynamic and regional dimension data were
recorded. A set of measurements was obtained within 1 minute. At 90
minutes of ischemia, measurements were repeated, and the
myocardium was reperfused for 120 minutes.
Control Group (n=7)
After control measurements, coronary inflow was reduced
to achieve a 90% reduction in regional myocardial function.
After control measurements, the myocardium was
subjected to 2 minutes of preconditioning ischemia with a 90%
reduction in regional myocardial function and then reperfused for 15
minutes. After reperfusion, coronary inflow was once again
reduced to the same level as during the preconditioning
ischemia. Thereafter, this protocol was identical to that of
the control group.
This protocol was identical to that of the IPc2 group, except
that the preconditioning ischemia was of 3-minute duration.
This protocol was identical to that of the IPc2 group, except
that the preconditioning ischemia was of 10-minute
duration.
Dea-IPc3 Group (n=7)
After control measurements, the intracoronary infusion
of adenosine deaminase was started 10 minutes before
ischemia and maintained until the end of the 90 minutes of
sustained ischemia. Except for the adenosine deaminase
infusion, this protocol was identical to that of the IPc3 group. In a
previous study using the same model, adenosine deaminase per se
did not alter infarct size resulting from 90 minutes of
ischemia, but it attenuated the preconditioning achieved by 10
minutes of ischemia and 15 minutes of
reperfusion.4
After control measurements, bradykinin B2
receptors were blocked by infusion of HOE 140. The infusion was started
30 minutes before ischemia and maintained until the end of the
90 minutes of sustained ischemia. Otherwise, this protocol was
identical to that of the control group.
After control measurements, the infusion of HOE 140 was started
and maintained until the end of the 90 minutes of sustained
ischemia. Otherwise, this protocol was identical to that of the
IPc3 group.
This protocol was identical to that of the HOE-IPc3 group,
except that the preconditioning ischemia was of 10-minute
duration.
After control measurements, the intracoronary infusion
of HOE 140 was started. After 20 minutes of HOE 140 infusion, the
additional adenosine deaminase infusion was started. Both
infusions were maintained until the end of the 90 minutes of sustained
ischemia. Otherwise, this protocol was identical to that of the
control group.
After control measurements, the intracoronary infusion
of HOE 140 was started. After 20 minutes of HOE 140 infusion, the
additional adenosine deaminase infusion was started. Both
infusions were maintained until the end of the 90 minutes of sustained
ischemia. Otherwise, this protocol was identical to that of the
IPc10 group.
Hemodynamic and functional
parameters were digitized and recorded over a 20-second
period during each microsphere injection by use of CORDAT II
software.14 Parameters reported are
left ventricular peak pressure, mean coronary
arterial pressure and blood flow, a regional work
index,15 and mean transmural blood flow.
Calculation of all parameters was done on a beat-to-beat
basis, and data were then averaged. Biochemical parameters
include the interstitial adenosine and bradykinin
concentrations at baseline, peak values during the preconditioning
cycle of ischemia/reperfusion, and peak values during the
sustained ischemia.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
Data on systemic hemodynamics, regional myocardial
function, and blood flow are summarized in Tables 1 and 2. Heart
rate was held constant by left atrial pacing at 104±4 bpm. Regional
myocardial function of the posterior control wall remained stable
throughout the experimental protocol in each group.
View this table:
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Table 1. Systemic Hemodynamics and Regional
Myocardial Function and Blood Flow
View this table:
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Table 2. Systemic Hemodynamics and Regional
Myocardial Function and Blood Flow
Systemic hemodynamics, regional myocardial blood
flow, and function were not different among groups under resting and
ischemic conditions (Table 1
). At
the end of the 15-minute reperfusion period, regional myocardial
function tended to be decreased in the IPc3 group but was significantly
depressed in the IPc2 and IPc10 groups.
The interstitial adenosine concentration was
significantly increased only with 10 minutes of preconditioning
ischemia (Figure 2). In contrast,
the interstitial bradykinin concentration increased to a
similar extent during 3 minutes and 10 minutes of preconditioning
ischemia (Figure 2).
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Figure 2. Interstitial adenosine and
bradykinin concentrations in swine undergoing 2 minutes (IPc2), 3
minutes (IPc3), or 10 minutes (IPc10) of preconditioning
ischemia and control group. Interstitial bradykinin
concentration remained unchanged with IPc2 but increased during IPc3
and IPc10 to a similar extent. During index ischemia (ISCH),
interstitial bradykinin concentration increased to a
similar extent in all groups of swine. Interstitial
adenosine concentration during preconditioning cycle was
significantly increased only with 10 minutes of preconditioning
ischemia. During ISCH, interstitial
adenosine concentration was increased in all groups of swine;
however, increase was more pronounced in control group and IPc2 group
vs IPc3 group and IPc10 group. *P<0.05 vs resting
conditions (REST), §P<0.05 vs IPc2 and IPc3.
The area at risk was comparable among the control, IPc2,
IPc3, and IPc10 groups, averaging 48.8±3.2%, 40.3±1.6%,
46.4±2.6%, and 42.6±1.3%, respectively. After 90 minutes of
sustained ischemia and 120 minutes of reperfusion, 16.7±3.4%
of the area at risk was infarcted. Infarct size remained unchanged
(21.9±7.0%) in the IPc2 group. Infarct size was reduced to 9.0±2.6%
in the IPc3 group (P<0.05 versus control and IPc2 groups)
and further reduced to 1.9±0.9% in the IPc10 group
(P<0.05 versus control, IPc2, and IPc3 groups). The slopes
of the relationships between infarct size and subendocardial blood flow
in the control and IPc2 groups were not significantly different (Figure 3). The slope was significantly reduced,
however, in the IPc3 group (P<0.05) and was decreased even
further in the IPc10 group (P<0.05 versus control, IPc2,
and IPc3 groups).
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Figure 3. Relationships of subendocardial blood flow and
infarct size in swine undergoing 90-minute index ischemia
without and with 2 minutes (IPc2), 3 minutes (IPc3), and 10 minutes
(IPc10) of preconditioning ischemia and 15 minutes of
reperfusion. Slopes of relationships between infarct size and
subendocardial blood flow in control group
(y=-322.9x+34.6, n=7,
r=0.95) and IPc2 group
(y=-420.3x+43.9, n=5,
r=0.98) were not significantly different. Slope was
significantly reduced, however, in IPc3 group
(y=-224.5x+21.9, n=7,
r=0.97, P<0.05). Slope was decreased
further in IPc10 group (y=-1.6x+2.0,
n=7, r=0.02, P<0.05 vs control, IPc2 and
IPc3 groups).
Systemic hemodynamics, regional myocardial blood
flow, and function were not different among groups under control and
ischemic conditions (Table 2).
Infusion of adenosine deaminase reduced the
interstitial adenosine concentration to values
<0.5 µmol/L. Thereafter, the interstitial
adenosine concentration remained at this reduced level
throughout the remaining experimental protocol (Figure 4). HOE 140 per se did not alter the
interstitial adenosine concentration. Whereas with
3 minutes of preconditioning ischemia, adenosine
concentration remained unchanged, it was significantly increased with
10 minutes of preconditioning ischemia. During the sustained
90-minute index ischemia, the interstitial
adenosine concentration increased to a similar extent in the
control and IPc3 groups, whereas in the IPc10 group, the increase in
the interstitial adenosine concentration during the
sustained ischemia was attenuated. HOE 140 and
adenosine deaminase infusion did not alter the
interstitial bradykinin concentration under control
conditions. During the preconditioning ischemia/reperfusion,
the interstitial bradykinin concentration was increased;
the increase in the interstitial bradykinin concentration
was not related to the duration of the preconditioning ischemia
(Figure 5). During the prolonged index
ischemia, the interstitial bradykinin concentration
increased to a similar extent in all groups of swine (Figure 5).
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Figure 4. Infusion of adenosine deaminase (Dea)
reduced interstitial adenosine concentrations to
values <0.5 µmol/L. Thereafter, interstitial
adenosine concentrations remained at this reduced level
throughout remaining experimental protocol. HOE 140 per se did not
alter interstitial adenosine concentration.
Interstitial adenosine concentration was not
altered with 3 minutes of preconditioning ischemia but was
significantly increased with 10 minutes of preconditioning
ischemia. During index ischemia,
interstitial adenosine concentrations increased to
a similar extent in control and IPc3 groups; in IPc10 group, increase
in interstitial adenosine concentration was
attenuated. *P<0.05 vs resting conditions (REST),
§P<0.05 vs all other groups.
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Figure 5. HOE 140 and adenosine deaminase (Dea)
infusion did not significantly alter interstitial
bradykinin concentrations. During preconditioning
ischemia/reperfusion period, interstitial
bradykinin concentrations increased; these increases in
interstitial bradykinin concentrations were not related to
duration of preconditioning ischemia. During prolonged index
ischemia, interstitial bradykinin concentration
increased to a similar extent in all groups of swine.
*P<0.05 vs REST.
The area at risk was comparable among the Dea-IPc3,
HOE-control, HOE-IPc3, HOE-IPc10, HOE-Dea-control, and HOE-Dea-IPc10
groups, averaging 46.6±2.7%, 47.4±2.5%, 42.9±2.9%, 45.2±3.3%,
48.7±4.6%, and 46.0±1.2%, respectively. Infusion of
adenosine deaminase did not attenuate the infarct size
reduction achieved by 3 minutes of ischemia and 15 minutes of
reperfusion (8.4±2.5%). In the presence of HOE 140, after the 90
minutes of sustained ischemia and 120 minutes of reperfusion,
14.0±1.8% of the area at risk was infarcted. With preconditioning by
3 minutes of ischemia and 15 minutes of reperfusion in the
presence of HOE 140, infarct size was no longer reduced (16.6±4.3%).
In contrast, the reduction in infarct size achieved by 10 minutes of
ischemia and 15 minutes of reperfusion was not affected by HOE
140 (3.5±1.1%, still P<0.05 versus control and
HOE-control groups). Combined infusion of HOE 140 and adenosine
deaminase slightly reduced infarct size (11.0±3.1%, P=NS
versus control group) and completely abolished the infarct size
reduction achieved by 10 minutes of ischemia and 15 minutes of
reperfusion (15.4±2.6%). The reduction in the slope of the
relationship between infarct size and subendocardial blood flow (Figure 6) by preconditioning with 3 minutes of
ischemia and 15 minutes of reperfusion was abolished by HOE 140
but not by adenosine deaminase infusion (still
P<0.05 versus control group). HOE 140, however, did not
alter the relationship between infarct size and subendocardial blood
flow with preconditioning by 10 minutes of ischemia and 15
minutes of reperfusion (still P<0.05 versus control group).
With combined infusion of HOE 140 and adenosine deaminase, the
relationships between infarct size and subendocardial blood flow in the
control group and the 10-minute ischemic preconditioning group
were not significantly different (Figure 7).
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Figure 6. Relationships of subendocardial blood flow and
infarct size in swine undergoing 90 minutes of index ischemia
without and with 3 minutes and 10 minutes of preconditioning
ischemia in presence of HOE 140. Adenosine deaminase
did not affect reduction in slope of relationships between infarct size
and subendocardial blood flow with preconditioning by 3 minutes of
ischemia (y=-279.2x+31.5, n=7,
r=0.74, P<0.05 vs control group).
Reduction in slope of relationships between infarct size and
subendocardial blood flow with preconditioning by 3 minutes of
ischemia was abolished by HOE 140
(y=-279.2x+31.5, n=9,
r=0.74). HOE 140, however, did not alter relationship
between infarct size and subendocardial blood flow achieved with
preconditioning by 10 minutes of ischemia
(y=-51.3x+6.4, n=8,
r=0.46, P<0.05 vs HOE-control and
HOE-IPc3 groups).
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Figure 7. Relationships of subendocardial blood flow and
infarct size in swine undergoing 90-minute index ischemia
without and with preconditioning by 10 minutes of ischemia in
presence of HOE 140 and adenosine deaminase (Dea). With
combined infusion of HOE 140 and Dea, relationships between infarct
size and subendocardial blood flow in control and preconditioned hearts
were not significantly different
(y=-201x+25.7, n=7,
r=0.87 vs y=-308x+34.4,
n=6, r=0.88).
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
Critique of Methods
The present experiments were performed in swine because
infarct development in this species, as a result of the sparsity of the
innate collateral circulation, most closely resembles that observed in
humans.16
Clearly, a threshold exists below which ischemic
preconditioning does not reduce infarct size, and in our preparation,
this threshold is somewhere between 2 and 3 minutes in duration of the
preconditioning ischemia. Also, in anesthetized
rabbits, 2 cycles of 2 minutes of coronary occlusion with 10
minutes of reperfusion each did not reduce infarct size after 30
minutes of coronary occlusion, but a single cycle of 5 minutes
of ischemia and 10 minutes of reperfusion reduced infarct size
significantly.10
The most obvious pool of adenosine is the breakdown
of cytosolic AMP in cardiomyocytes (for review, see
Reference 1919 ). In previous studies, the interstitial
adenosine concentration increased no earlier than after 5
minutes of ischemia.20 In accordance with
previously published data in anesthetized
dogs,21 rabbits,22 and
pigs,23 the interstitial
adenosine concentration during the sustained ischemia
was attenuated in the 3-minute and 10-minute ischemic
preconditioning groups. Such attenuation of the increase in the
interstitial adenosine concentration is also
observed when ischemic preconditioning is abolished by
adenosine receptor blockade, and therefore, it is not a
reflection of the cardioprotective effect.22
The results of the present study support the threshold
concept proposed by Downey and coworkers.6 In
accordance with their study, bradykinin was of major importance only
during a less intense preconditioning stimulus, ie, a shorter duration
of preconditioning ischemia, whereas during a more intense
preconditioning stimulus, ie, a more prolonged period of
preconditioning ischemia, adenosine was of greater
importance. Also, the additive interaction of triggers was confirmed in
the present study, in that only combined blockade of the bradykinin
B2 receptor by HOE 140 and increased breakdown of
endogenous adenosine by adenosine deaminase
completely abolished the infarct size reduction achieved by
preconditioning with 10 minutes of ischemia and 15 minutes of
reperfusion.
Acknowledgments
This study was supported by the German Research Foundation (He
1320/8–2 and 9–1). We thank Claus Martin, PhD, for the chemical
analyses and Petra Gres, Ursula Prägler, and Anita van de
Sand for their technical support.
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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  P. Ferdinandy, R. Schulz, and G. F. Baxter Interaction of Cardiovascular Risk Factors with Myocardial Ischemia/Reperfusion Injury, Preconditioning, and Postconditioning Pharmacol. Rev., December 1, 2007; 59(4): 418 - 458. [Abstract] [Full Text] [PDF]
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 D. Kohler, T. Eckle, M. Faigle, A. Grenz, M. Mittelbronn, S. Laucher, M. L. Hart, S. C. Robson, C. E. Muller, and H. K. Eltzschig CD39/Ectonucleoside Triphosphate Diphosphohydrolase 1 Provides Myocardial Protection During Cardiac Ischemia/Reperfusion Injury Circulation, October 16, 2007; 116(16): 1784 - 1794. [Abstract] [Full Text] [PDF]
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S. P. Loukogeorgakis, R. Williams, A. T. Panagiotidou, S. K. Kolvekar, A. Donald, T. J. Cole, D. M. Yellon, J. E. Deanfield, and R. J. MacAllister Transient Limb Ischemia Induces Remote Preconditioning and Remote Postconditioning in Humans by a KATP Channel Dependent Mechanism Circulation, September 18, 2007; 116(12): 1386 - 1395. [Abstract] [Full Text] [PDF]
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 C. Penna, D. Mancardi, R. Rastaldo, G. Losano, and P. Pagliaro Intermittent activation of bradykinin B2 receptors and mitochondrial KATP channels trigger cardiac postconditioning through redox signaling Cardiovasc Res, July 1, 2007; 75(1): 168 - 177. [Abstract] [Full Text] [PDF]
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 M. A. Leesar, H. Jneid, X.-L. Tang, and R. Bolli Pretreatment with intracoronary enalaprilat protects human myocardium during percutaneous coronary angioplasty. J. Am. Coll. Cardiol., April 17, 2007; 49(15): 1607 - 1610. [Abstract] [Full Text] [PDF]
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 A. Skyschally, P. Gres, S. Hoffmann, M. Haude, R. Erbel, R. Schulz, and G. Heusch Bidirectional Role of Tumor Necrosis Factor-{alpha} in Coronary Microembolization: Progressive Contractile Dysfunction Versus Delayed Protection Against Infarction Circ. Res., January 5, 2007; 100(1): 140 - 146. [Abstract] [Full Text] [PDF]
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D. J. Hausenloy, M. M. Mocanu, and D. M. Yellon Is This Truly Ischemic Preconditioning? Circ. Res., August 18, 2006; 99(4): e11 - e11. [Full Text] [PDF]
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D. Ramzy, V. Rao, and R. D. Weisel Clinical applicability of preconditioning and postconditioning: The cardiothoracic surgeons's view Cardiovasc Res, May 1, 2006; 70(2): 174 - 180. [Full Text] [PDF]
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E. R. Gross and G. J. Gross Ligand triggers of classical preconditioning and postconditioning Cardiovasc Res, May 1, 2006; 70(2): 212 - 221. [Abstract] [Full Text] [PDF]
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 M. Morihira, N. Hasebe, E. Baljinnyam, K. Sumitomo, T. Matsusaka, K. Izawa, T. Fujino, J. Fukuzawa, and K. Kikuchi Ischemic preconditioning enhances scavenging activity of reactive oxygen species and diminishes transmural difference of infarct size Am J Physiol Heart Circ Physiol, February 1, 2006; 290(2): H577 - H583. [Abstract] [Full Text] [PDF]
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N. V. Solenkova, V. Solodushko, M. V. Cohen, and J. M. Downey Endogenous adenosine protects preconditioned heart during early minutes of reperfusion by activating Akt Am J Physiol Heart Circ Physiol, January 1, 2006; 290(1): H441 - H449. [Abstract] [Full Text] [PDF]
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Z. Cai and G. L. Semenza PTEN Activity Is Modulated During Ischemia and Reperfusion: Involvement in the Induction and Decay of Preconditioning Circ. Res., December 9, 2005; 97(12): 1351 - 1359. [Abstract] [Full Text] [PDF]
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 T. H. Adair Growth regulation of the vascular system: an emerging role for adenosine Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2005; 289(2): R283 - R296. [Abstract] [Full Text] [PDF]
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K. Aouam, R. Tissier, P. Bruneval, C. Mandet, A. Berdeaux, and B. Ghaleh Preconditioning of salvaged myocardium in conscious rabbits with postinfarction dysfunction Am J Physiol Heart Circ Physiol, June 1, 2005; 288(6): H2763 - H2769. [Abstract] [Full Text] [PDF]
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 J. Feng, C. Bianchi, J. Li, and F. W. Sellke Bradykinin Preconditioning Preserves Coronary Microvascular Reactivity During Cardioplegia-Reperfusion Ann. Thorac. Surg., March 1, 2005; 79(3): 911 - 916. [Abstract] [Full Text] [PDF]
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 B. J Epstein and J. G Gums Angiotensin Receptor Blockers versus ACE Inhibitors: Prevention of Death and Myocardial Infarction in High-Risk Populations Ann. Pharmacother., March 1, 2005; 39(3): 470 - 480. [Abstract] [Full Text] [PDF]
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D. A. Liem, M. te Lintel Hekkert, O. C. Manintveld, F. Boomsma, P. D. Verdouw, and D. J. Duncker Myocardium tolerant to an adenosine-dependent ischemic preconditioning stimulus can still be protected by stimuli that employ alternative signaling pathways Am J Physiol Heart Circ Physiol, March 1, 2005; 288(3): H1165 - H1172. [Abstract] [Full Text] [PDF]
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M.W. Broadhead, R.K. Kharbanda, M.J. Peters, and R.J. MacAllister KATP Channel Activation Induces Ischemic Preconditioning of the Endothelium in Humans In Vivo Circulation, October 12, 2004; 110(15): 2077 - 2082. [Abstract] [Full Text] [PDF]
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M. Wei, X. Wang, P. Kuukasjarvi, J. Laurikka, T. Rinne, E.-L. Honkonen, and M. Tarkka Bradykinin preconditioning in coronary artery bypass grafting Ann. Thorac. Surg., August 1, 2004; 78(2): 492 - 497. [Abstract] [Full Text] [PDF]
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C.-H. Huang, J.-S. Wang, S.-C. Chiang, Y.-Y. Wang, S.-T. Lai, and Z.-C. Weng Brief pressure overload of the left ventricle preconditions rabbit myocardium against infarction Ann. Thorac. Surg., August 1, 2004; 78(2): 628 - 633. [Abstract] [Full Text] [PDF]
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A. Skyschally, R. Schulz, P. Gres, I. Konietzka, C. Martin, M. Haude, R. Erbel, and G. Heusch Coronary microembolization does not induce acute preconditioning against infarction in pigs--the role of adenosine Cardiovasc Res, August 1, 2004; 63(2): 313 - 322. [Abstract] [Full Text] [PDF]
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C. Weinbrenner, F. Schulze, L. Sarvary, and R. H Strasser Remote preconditioning by infrarenal aortic occlusion is operative via {delta}1-opioid receptors and free radicals in vivo in the rat heart Cardiovasc Res, February 15, 2004; 61(3): 591 - 599. [Abstract] [Full Text] [PDF]
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