K + Currents in Human Coronary Artery Vascular Smooth Muscle Cells

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Abstract
K+ channels and their currents are important in vascular tone regulation and are potential therapeutic targets; however, K+ channels in human coronary artery vascular smooth muscle cells (VSMCs) have received little attention. We examined K+ currents in freshly isolated VSMCs from human coronary arteries (n=368 from 32 human hearts) with conventional patch-clamp or perforated-patch techniques with nystatin. We detected four different K+ currents: (1) the delayed rectifier K+ current, IK(dr); (2) the Ca2+-activated K+ current, IK(Ca); (3) the nonrectifying noninactivating outward ATP-dependent K+ current, IK(ATP); and (4) the spontaneous transient outward K+ current, IK(STOC). K+ channels underlying spontaneous transient outward currents probably represent a single clustered population of Ca2+-activated K+ channels functionally associated with Ca2+ release channels in the sarcoplasmic reticulum. Inwardly rectifying K+ currents were not observed. K+ currents were unevenly distributed in that they w...