PROPERTIES OF SINGLE POTASSIUM CHANNELS IN GUINEA-PIG HEPATOCYTES

The patch-clamp technique oi cell-attached and inside-out configuratio ns was used to study the single potassium channels in isolated guinea pig hepatocytes. The single potassium channels in isolated guinea pig hepatocytes were recorded at different K+ concentrations. A linear sin gle-channel current-voltage relationship was obtained at the voltage r ange of -80 to -20 mV with slope conductance of 70 +/- 6 pS (n = 10). Under symmetrical high K+ concentration of 148 mM in the cell-attached patch membrane, the I-V curve exhibited a mild inward rectification a t potentials positive to +20 mV. The values of reversal potential was +5 +/- 2 mV (n = 10). When the external potassium concentration ([K+]( o)) was decreased to 74 mM and 20 mM, the slope conductance was decrea sed to 48 +/- 2 pS (n = 4) and 24 +/- 3 pS (n = 3), respectively. The reversal potential was changed by 58 mV for a tenfold change in [K+](o ), indicating that this channel was highly selective for K+. Open prob abilities (P-o) of the channel were 73-93% without apparent voltage de pendence. The distributions of open time of the channels were fitted t o two exponentials, while those of closed time were fitted to three ex ponentials, exhibiting no voltage dependence. The success rate of K+ c hannel activity to be recorded was 28% at room temperature, and there were no increases in the success rate nor in the channel opening proba bilities at a temperature of 34-36 degrees C. P-o in inside-out patche s was not changed by application of 1 mu M Ca2(+) nor 1 mM Mg2+ to the internal side of patch membranes. It is concluded that a novel type o f the K+ channels in guinea pig hepatocytes had different properties o f slope conductance, channel kinetics, and sensitivity to [Ca2+](i), f rom those in other species. (C) 1994 Wiley-Liss, Inc.