VOLTAGE-DEPENDENT POTASSIUM CHANNELS IN WHITE ADIPOCYTES

Macroscopic membrane currents of white adipocytes were studied using t he whole-cell variant of the patchclamp technique. These cells were ob tained by differentiating preadipocytes from rat epididymal tissue. In all differentiated cells outward currents exhibiting sigmoidal activa tion kinetics were observed with amplitudes ranging from 0.5 to 6 nA. The outward current showed activation thresholds at approximately -25 to -35 mV. The ion channels underlying the macroscopic current were hi ghly selective for K+. Their selectivity was typical for K+ channels, with relative permeabilities of K+ > NH4+ > Cs+, Na+. The potassium cu rrent was blocked by tetraethylammonium. 4-aminopyridine, barium and c obalt. These results demonstrate the existence of voltage dependent po tassium channels in mature white adipose cells. (C) 1996 Academic Pres s, Inc.