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Pharmacological activation of KCa3.1/KCa2.3 channels produces endothelial hyperpolarization and lowers blood pressure in conscious dogs
Author(s) -
Damkjaer Mads,
Nielsen Gorm,
Bodendiek Silke,
Staehr Mette,
Gramsbergen JanBert,
de Wit Cor,
Jensen Boye L,
Simonsen Ulf,
Bie Peter,
Wulff Heike,
Köhler Ralf
Publication year - 2012
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2011.01546.x
Subject(s) - vasodilation , electrical impedance myography , blood pressure , hyperpolarization (physics) , medicine , endothelium , mesenteric arteries , baroreceptor , chemistry , endothelium derived hyperpolarizing factor , cardiology , electrophysiology , endocrinology , heart rate , artery , repolarization , organic chemistry , nuclear magnetic resonance spectroscopy
BACKGROUND AND PURPOSE In rodents, the endothelial KCa channels, KCa3.1 and KCa2.3, have been shown to play a crucial role in initiating endothelium‐derived hyperpolarizing factor (EDHF) vasodilator responses. However, it is not known to what extent these channels are involved in blood pressure regulation in large mammals, which would also allow us to address safety issues. We therefore characterized canine endothelial KCa3.1 and KCa2.3 functions and evaluated the effect of the KCa3.1/KCa2.3 activator SKA‐31 on blood pressure and heart rate in dogs. EXPERIMENTAL APPROACH Canine endothelial KCa3.1/KCa2.3 functions were studied by patch‐clamp electrophysiology and wire myography in mesenteric arteries. Systemic cardiovascular actions of acute SKA‐31 administration were monitored in conscious, unstressed beagle dogs. KEY RESULTS Mesenteric endothelial cells expressed functional KCa3.1 and KCa2.3 channels that were strongly activated by SKA‐31. SKA‐31 hyperpolarized the endothelial membrane and doubled endothelial hyperpolarization‐dependent vasodilator responses in mesenteric arteries. SKA‐31 (2 mg·kg −1 , i.v.) rapidly decreased the MAP by 28 ± 6 mmHg; this response was transient (8 ± 1 s), and the initial drop was followed by a fast and pronounced increase in HR (+109 ± 7 beats min −1 ) reflecting baroreceptor activation. SKA‐31 significantly augmented similar transient depressor responses elicited by ACh (20 ng·kg −1 ) and doubled the magnitude of the response over time. CONCLUSIONS AND IMPLICATIONS Activation of endothelial KCa3.1 and KCa2.3 lowers arterial blood pressure in dogs by an immediate electrical vasodilator mechanism. The results support the concept that pharmacological activation of these channels may represent a potential unique endothelium‐specific antihypertensive therapy.