Effects of copper on T-type Ca2+ channels in mouse spermatogenic cells

Low voltage-activated, rapidly inactivating T-type Ca2+ channels are found in a variety of cells, where they regulate electrical activity and Ca2+ entry. In whole-cell patch-clamp recordings from mouse spermatogenic cells, trace element copper (Cu2+) inhibited T-type Ca2+ current (IT-Ca) with IC50 of 12.06 microM. Inhibition of IT-Ca by Cu2+ was concentration-dependent and mildly voltage-dependent. When voltage stepped to -20 mV, Cu2+ (10 microM) inhibited IT-Ca by 49.6 +/- 4.1%. Inhibition of IT-Ca by Cu2+ was accompanied by a shift of -2.23 mV in the voltage dependence of steady-state inactivation. Cu2+ upshifted the current-voltage (I-V) curve. To know the change of the gating kinetics of T-type Ca2+ channels, we analyzed the effect of Cu2+ on activation, inactivation, deactivation and reactivation of T-type Ca2+ channels. Since T-type Ca2+ channels are a key component in capacitation and the acrosome reaction, our data suggest that Cu2+ can affect male reproductive function through T-type Ca2+ channels as a preconception contraceptive material.