Exposure to ethanol during capacitation impairs the fertilizing ability of human spermatozoa in vitro

To validate earlier findings, mainly in laboratory animals, the effect of ethanol on the fertilizing ability of human spermatozoa has been investigated. Ethanol added to the capacitation medium reduced the penetration of zona-free hamster eggs by human spermatozoa in a dose-dependent manner at concentrations from 50 to 500 mg % (0.05-0.5%). Fertilizing capacity was at least partially restored by washing in ethanol-free medium. Ethanol exposure before capacitation had a slight stimulatory effect on the penetration of spermatozoa into zona-free hamster ova. The motility of spermatozoa was not altered significantly, either quantitatively or qualitatively, by the presence of ethanol in the capacitation medium. These results suggest that the decrease in fertilizing ability of spermatozoa induced by ethanol during capacitation is due to a specific action on the capacitation process.