K channels and the regulation of vascular smooth muscle tone.

VSMCs in resistance arteries and arterioles express a diverse array of K channels with members of the K 1, K 2 and K 7 families being particularly important. Members of the K channel family: (i) are highly expressed in VSMCs; (ii) are active at the resting membrane potential of VSMCs in vivo (-45 to -30 mV); (iii) contribute to the negative feedback regulation of VSMC membrane potential and myogenic tone; (iv) are activated by cAMP-related vasodilators, hydrogen sulfide and hydrogen peroxide; (v) are inhibited by increases in intracellular Ca and vasoconstrictors that signal through G -coupled receptors; (vi) are involved in the proliferative phenotype of VSMCs; and (vii) are modulated by diseases such as hypertension, obesity, the metabolic syndrome and diabetes. Thus, K channels participate in every aspect of the regulation of VSMC function in both health and disease.