on April 20, 2009
Published online before print April 20, 2009, doi: 10.1161/CIRCULATIONAHA.108.846634
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Submitted on December 22, 2008
From the Department of Internal Medicine/Nephrology, Philipps University, Marburg, Germany (S.B., A.K., C.B., B.P.K., M.K., A.H., I.G., J.H., R.K.); Department of Physiology, University of Lübeck, Lübeck, Germany (V.J.S., S.E.W., C.d.W.); Division of Nephrology, Albert Einstein College of Medicine, Bronx, NY (H.S.); Vollum Institute, Oregon Health and Science University, Portland (C.T.B., J.P.A.); and Department of Pharmacology, University of California, Davis (H.W.). * To whom correspondence should be addressed. E-mail: rkoehler{at}med.uni-marburg.de.
Background—It has been proposed that activation of endothelial SK3 (KCa2.3) and IK1 (KCa3.1) K+ channels plays a role in the arteriolar dilation attributed to an endothelium-derived hyperpolarizing factor (EDHF). However, our understanding of the precise function of SK3 and IK1 in the EDHF dilator response and in blood pressure control remains incomplete. To clarify the roles of SK3 and IK1 channels in the EDHF dilator response and their contribution to blood pressure control in vivo, we generated mice deficient for both channels. Methods and Results—Expression and function of endothelial SK3 and IK1 in IK1-/-/SK3T/T mice was characterized by patch-clamp, membrane potential measurements, pressure myography, and intravital microscopy. Blood pressure was measured in conscious mice by telemetry. Combined IK1/SK3 deficiency in IK1-/-/SK3T/T (+doxycycline) mice abolished endothelial KCa currents and impaired acetylcholine-induced smooth muscle hyperpolarization and EDHF-mediated dilation in conduit arteries and in resistance arterioles in vivo. IK1 deficiency had a severe impact on acetylcholine-induced EDHF-mediated vasodilation, whereas SK3 deficiency impaired NO-mediated dilation to acetylcholine and to shear stress stimulation. As a consequence, SK3/IK1-deficient mice exhibited an elevated arterial blood pressure, which was most prominent during physical activity. Overexpression of SK3 in IK1-/-/SK3T/T mice partially restored EDHF- and nitric oxide–mediated vasodilation and lowered elevated blood pressure. The IK1-opener SKA-31 enhanced EDHF-mediated vasodilation and lowered blood pressure in SK3-deficient IK1+/+/SK3T/T (+doxycycline) mice to normotensive levels. Conclusions—Our study demonstrates that endothelial SK3 and IK1 channels have distinct stimulus-dependent functions, are major players in the EDHF pathway, and significantly contribute to arterial blood pressure regulation. Endothelial KCa channels may represent novel therapeutic targets for the treatment of hypertension.
Accepted on March 3, 2009
Genetic Deficit of SK3 and IK1 Channels Disrupts the Endothelium-Derived Hyperpolarizing Factor Vasodilator Pathway and Causes Hypertension
Sebastian Brähler ,
Key words: blood pressure • endothelium-derived factors • ion channels • KCa3.1 protein, mouse
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Circulation 2009 119: 2295-2296.
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