AN ATP, CALCIUM AND VOLTAGE SENSITIVE POTASSIUM CHANNEL IN PORCINE CORONARY-ARTERY SMOOTH-MUSCLE CELLS

There is increasing interest in the roles played by potassium channels of smooth muscle in protecting against ischemic and anoxic insults. Hence, potassium-selective channels were studied in freshly dispersed porcine coronary artery smooth muscle cells using the inside-out variant of the patch-clamp technique. The most abundant potassium channel had a conductance of 148 pS in a 5.4 140 mM K+ gradient, at 0 mV, and was regulated by cytoplasmic ATP (0.05 - 3.0 mM), cytoplasmic Ca2+ (0.1-10 μM) and voltage. ATP and AMP-PNP (0.5 mM) reduced the probability of channel opening (P0) by 87 and 92%, respectively. This inhibition was partially reversed by the addition of 0.5 mM ADP. ADP on its own (2 mM) reduced P0 by 46%. It appears, therefore, that this channel shares properties with both the ATP-sensitive and the calcium-regulated potassium channels, raising the possibility that it plays a central role in the regulation of coronary blood flow. © 1990.