Inhibition of Ca2+ channels in mouse spermatogenic cells by male antifertility compounds from Tripterygium wilfordii Hook. f.

The male antifertility effect of a water-chloroform extract (GTW) from the root xylem of Tripterygium wilfordii has attracted worldwide interest. In the present study, by using whole-cell recording, the effects of GTW and two isolated monomers from GTW, demethylzeylasteral and L-epicatechin. on the T-type Ca2+ channels in mouse spermatogenic cells were investigated. The results showed that each of them concentration-dependently and partially reversibly inhibited T-type Ca2+ current in the cells. The IC50 of GTW and demethylzeylasteral were approximate, while L-epicatechin inhibited the channels at a much higher concentration. The voltage dependence of the inhibitory effect and the changes in activation and inactivation time constants after application of these compounds were also examined. These data suggest that the inhibition of T-type Ca2+ Currents could be responsible for the antifertility activity of these compounds. (C) 2002 Elsevier Science Inc. All rights reserved.