Role of potassium channels in regulation of rat coronary arteriole tone.
Activity of potassium (K(+)) channels plays a key role in regulating arterial tone and therefore blood flow. But little is known about the roles of K(+) channels in the coronary arterioles. The aim of the present study was to investigate the influences of several potassium channel blockers on resting vascular tone in isolated rat coronary arteriole. The coronary arterioles were carefully dissected, cannulated and pressurized. The inner diameter of vessels was recorded by a computerized diameter tracking system and the effects of K(+) channels on the development of vascular myogenic tone was tested by application of various K(+) channel inhibitors. Inhibition of voltage-dependent K(+) (K(V)) channels and inward rectifier K(+) (K(ir)) channels significantly increased the tone constriction. But inhibition of Ca(2+)-activated K(+) (K(Ca)) channels and ATP-sensitive K(+) (K(ATP)) channels had no effect on the resting tone. In addition, inhibition of nitric oxide synthase (NOS) further decreased the tone diameter. Combined inhibition of K(V), K(ir) and NOS induced the strongest tone constriction. Our results suggested that activity of K(V) and K(ir) channels, and basal nitric oxide (NO) contribute to the myogenic tone in rat coronary arteriole under resting conditions, but basal NO may not contribute to the activation of K(V) and K(ir) channels. K(Ca) and K(ATP) channels are likely to have a very low open probability under normal conditions.
Wu
Guo-Bao
GB
Department of Medicine, 2nd Xiangya Hospital of Central South University, Changsha, Hunan, PR China.
Zhou
En-Xiang
EX
Qing
Du-Xin
DX
Li
Jun
J
D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D004727:Endothelium / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D004791:Enzyme Inhibitors; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase