Long-term exposure of the male mouse to lead: effects on fertility

Sexually mature male mice, exposed to lead in the drinking water for 3 months, attained a mean blood level of 32 micrograms/100 ml. In control mice, given deionized water, blood lead levels were less than 0.5 microgram/100 ml. At the end of the exposure period, each male was caged with three untreated females. On Day 17 after mating, the frequency of pregnant females and the number of fetuses and resorptions were recorded. Females without implantations were significantly more numerous (P less than 0.05) in the group that had been mated with the lead-exposed males. The frequencies of resorptions and fetal malformations were similar in the two groups. The two groups of males were compared with respect to body weight, plasma level of testosterone, number of epididymal sperms, and weight of reproductive organs. No statistically significant differences were found. Increased tissue concentrations of lead were noted for all the male reproductive organs, as well as the hypothalamus. It cannot be decided at present whether the decrease in the number of pregnant females was due to a reduction in the ability of spermatozoa from the lead-exposed males to fertilize or to a preimplantation loss of fertilized ova.