Voltage-clamped membrane currents have been investigated from whole-cell patch-clamp recordings performed on single Leydig cells isolated from the adult rat testis. Two outward membrane currents were evoked by depolarizing voltage steps. A potassium current was recorded in cells dialyzed with low (10−9−10−8 M) calcium media. This current was decreased by TEA (10 mM). A chloride current was recorded in cells dialyzed with high (10−7 − 10−6 M) calcium media. This current was decreased by an external exposure to glutamate. Comparison of the currents at low and high internal calcium concentrations suggests that an increase of the intracellular calcium activates a chloride current.
