PHYSIOLOGICAL ROLES AND PROPERTIES OF POTASSIUM CHANNELS IN ARTERIAL SMOOTH-MUSCLE

This review examines the properties and roles of the four types of Kchannels that have been identified in the cell membrane of arterial sm ooth muscle cells. 1) Voltage-dependent K+ (Kv) channels increase thei r activity with membrane depolarization and are important regulators o f smooth muscle membrane potential in response to depolarizing stimuli . 2) Ca2+-activated K+ (K-Ca) channels respond to changes in intracell ular Ca2+ to regulate membrane potential and play an important role in the control of myogenic tone in small arteries. 3) Inward rectifier K + (K-IR) channels regulate membrane potential in smooth muscle cells f rom several types of resistance arteries and may be responsible for ex ternal K+-induced dilations. 4) ATP-sensitive K+ (K-ATP) channels resp ond to changes in cellular metabolism and are targets of a variety of vasodilating stimuli. The main conclusions of this review are: 1) regu lation of arterial smooth muscle membrane potential through activation or inhibition of K+ channel activity provides an important mechanism to dilate or constrict arteries; 2) K-V, K-Ca, K-IR, and K-ATP channel s serve unique functions in the regulation of arterial smooth muscle m embrane potential; and 3) K+ channels integrate a variety of vasoactiv e signals to dilate or constrict arteries through regulation of the me mbrane potential in arterial smooth muscle.