Electrophysiological studies of the action of gonadotropins on Leydig and Sertoli cells from rat testis.

Using intracellular microelectrode recordings, it was observed that FSH caused the hyperpolarization of cultured Sertoli cells from the testis of 17-day old rats; this hyperpolarization was related to the activation of a Na/K pump and an increase in Na/Ca influx and K efflux. The effect was irreversible and mediated by cAMP. Some other results suggested an initial effect of FSH on the junctional complex between the Sertoli cells and then its calcium dependence. Voltage-clamped membrane currents were investigated from whole-cell patch clamp recordings performed on single Leydig cells isolated from adult rat testis. Two outward currents were evoked by depolarizing voltage steps: a potassium current recorded in cells dialyzed with low-calcium media (10(-9)-10(-8) M) and a chloride current recorded in cells dialyzed with high-calcium media (10(-7)-10(-6) M). These responses to modifications of intracellular calcium were not affected by hCG. However, this hormone induced an early change of the K current to a Cl current when the cells were dialyzed by a low-buffered EGTA-calcium medium. These results suggest that hCG stimulation involved the blockade of a potassium current and the activation of a chloride current through an increase of intracellular calcium.