CHARACTERIZATION OF K-GLANDS( AND CA2+ IONIC CURRENTS IN GLOMERULOSA CELLS FROM HUMAN ADRENAL)

Ionic currents of primary cultured glomerulosa cells from human adrena l glands were studied with the patch-clamp technique. Two types of out ward K+ currents and two types of inward Ca2+ currents were described. The transient outward K+ current activated at potential positive to - 40 mV and demonstrated a marked time-dependent inactivation. It was bl ocked by 4-aminopyridine but not tetraethylammonium. A second type of outward current activated rapidly at the depolarization onset and then increased slowly with no time-dependent inactivation. The transient i nward T-tqpe Ca2+ current was activated for potential positive to -60 mV with a maximal current amplitude at -30 mV and zero current voltage at +40 mV; it was completely inactivated for membrane potential posit ive to -40 mV. The pharmacological studies of the T-type channel showe d that Ni2+ was a potent blocker but that the channel was not sensitiv e to dihydropyridine. The long-lasting inward Ca2+ current was activat ed for potentials positive to -20 mV with a maximum current amplitude at +70 mV. This current was increased by the agonist Bay K 8644 and bl ocked by the antagonist nifedipine; in addition, it was blocked by Cd2 + but less sensitive to Ni2+. This study revealed that glomerulosa cel ls from human adrenal demonstrated the presence of K+ and Ca2+ current s similar to those found in rat and bovine cells. Moreover, the main s timuli of aldosterone secretion, ACTH and angiotensin II, induce an in crease in aldosterone secretion which is inhibited in a Ca2+-free exte rnal medium.