Abstract

Ethanol is generally regarded as a reproductive toxin. However, the mechanism(s) of ethanol-induced infertility remain poorly understood. As male fertility depends upon the ability of spermatozoa to fertilize ova, it was the purpose of the present study to examine the effects of chronic ethanol treatment on several parameters related to sperm fertility. Male C57Bl/6J mice of proven fertility were administered liquid diets as follows: 5% (v/v) ethanol for either 1) 5 weeks; 2) 10 weeks; 3) 20 weeks; or 4) 6% (v/v) ethanol for 5 weeks. After each treatment, epididymal spermatozoa were evaluated with respect to quantity, motility, morphology and the ability to fertilize. A biphasic effect on sperm content was noted: 5- and 10-week treatments with 5% ethanol increased content by 80 and 65%, respectively, whereas 20-week treatment with 5% ethanol and 5-week treatment with 6% ethanol decreased content by 52 and 71%, respectively. Although the proportion of motile spermatozoa was unaffected by ethanol, average forward progression velocity was reduced, the effect being dependent on ethanol dose and duration of exposure. Similarly, the frequency of abnormal spermatozoa was increased; 20-week treatment with 5% ethanol and 5-week treatment with 6% ethanol increased the frequency of sperm morphological anomalies by 50 and 40%, respectively. Fertility of spermatozoa was reduced as a function of ethanol dose and duration of exposure. The ability of sperm to fertilize mouse ova in vitro was reduced by 34% (P less than .02) and 62% (P less than .001) subsequent to 20-week treatment with 5% ethanol and 5-week treatment with 6% ethanol, respectively. An animal model has been developed which describes ethanol-induced male infertility. The degree of reproductive impairment varies with the amount of ethanol ingested, and the duration of ethanol exposure. The continuum of effects should make possible the evaluation of putative mechanisms of male sterility resulting from chronic ethanol consumption.