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 Ca²⁺ channels; therefore, when K⁺ channel activity changes, Ca²⁺ influx and arterial tone change. This is why both Ca²⁺ channel blockers and K⁺ channel openers have such profound effects on coronary blood flow; the former directly inhibits Ca²⁺ influx through L-type Ca²⁺ channels, while the latter indirectly inhibits Ca²⁺influx by hyperpolarizing E_m and reducing Ca²⁺ 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.