Involvement of external potassium in membrane potential of smooth muscle cells of human allantochorial placental vessels

Abstract

The membrane potential (Um) of smooth muscle cells of human placental vessels is observed in survival medium with varying K + concentration. In a K +-free medium, the membrane is hyperpolarized, whereas from 8 mM K + in the medium, a depolarization is observed. There is a linear correlation between potential variation and [K +] 0 ( r=0.98) with a slope of 0.412±0.093 mV/mM K +. Moreover, a K + depolarization followed by a rinsing indicates the membrane of smooth muscle cells is predepolarized in normal medium. These results show the implication of external K + in the membrane potential level and induce the presence of delayed rectifier K + channels and the absence of inward rectifier K + channels in the membrane of smooth muscle cells of human placental vessels.