Role of potassium channels in coronary vasodilation.

K(+) channels in coronary arterial smooth muscle cells (CASMC) determine the resting membrane potential (E(m)) and serve as targets of endogenous and therapeutic vasodilators. E(m) in CASMC is in the voltage range for activation of L-type Ca(2+) channels; therefore, when K(+) channel activity changes, Ca(2+) influx and arterial tone change. This is why both Ca(2+) channel blockers and K(+) channel openers have such profound effects on coronary blood flow; the former directly inhibits Ca(2+) influx through L-type Ca(2+) channels, while the latter indirectly inhibits Ca(2+) influx by hyperpolarizing E(m) and reducing Ca(2+) channel activity. K(+) channels in CASMC play important roles in vasodilation to endothelial, ischemic and metabolic stimuli. The purpose of this article is to review the types of K(+) channels expressed in CASMC, discuss the regulation of their activity by physiological mechanisms and examine impairments related to cardiovascular disease.