Voltage-dependent calcium current with properties of T-type current in Sertoli cells from immature rat testis in primary cultures

We have applied the whole-cell configuration of the patch-clamp technique to investigate calcium currents in Sertoli cells from immature rat testis in primary culture. Cesium-filled pipettes were used to block potassium currents. In the presence of 10 mM extracellular calcium (Ca2+), depolarizations elicited transient inward currents in the range -70 to +10 mV with a maximal amplitude of -1.3 pA/pF at -30 mV. This component activated in the range -70 to -20 mV (V-0.5 = -42 mV) and inactivated in the range -75 to -45 mV (V-0.5 = -61 mV). Currents were not modified when barium (Ba2+) was substituted for Ca2+. They were suppressed by Ca2+-free solutions, insensitive to Bay K 8644 (an L-type channel opener), and inhibited by 1 mM cobalt, 10 mu M nickel, 10 mu M isradipine, and 1-10 mu M omega conotoxine GVIA (four calcium-channel blockers). We conclude that calcium channels with the properties of T-type calcium channels of excitable cells are located in the membrane of immature Sertoli cells in primary cultures. Because these channels do not appear to be directly sensitive to FSH, their involvement in calcium movements remains to be determined.