Electrophysiological study on the high K+ sensitivity of rat glomerulosa cells

 Elevation of extracellular potassium concentration by as little as some tenth of mM activates rat adrenal glomerulosa cells. In the present study some factors responsible for this high K⁺ sensitivity were examined. Using whole-cell voltage-clamp technique we found that both T-type and L-type voltage-dependent Ca²⁺ channels have very low threshold potential (–71 and –58 mV, resp.). By means of patch-clamp technique combined with single-cell fluorimetry we also provided evidence that the activation of I_gl, a K⁺-activated inward rectifying current is associated with Ca²⁺ influx. Both the low activation threshold of voltage-dependent Ca²⁺ channels and the function of I_gl contribute to the exceptional K⁺ sensitivity of the glomerulosa cells. Received: 30 September 1997 / Accepted: 4 November 1997