Effects of treatment with methyl methanesulfonate during meiotic and postmeiotic stages and maturation of spermatozoa in mice.

DNA damage and its related effects were quantitatively measured in germ cells at various meiotic and postmeiotic stages in male mice treated with methyl methanesulfonate (MMS). Unscheduled DNA synthesis (UDS) took place most efficiently in germ cell stages from middle to late spermatocytes at the time of MMS treatment, and essentially no UDS was detected in the stages from late spermatid to maturing spermatozoa, suggesting the absence of DNA repair in late spermatids and maturing spermatozoa. Late spermatids and immature spermatozoa were, on the other hand, most sensitive to MMS in producing DNA single-strand breaks (SSB) as well as chromosome aberrations in eggs fertilized by the treated males. The storage of the spermatozoa in the reproductive tract appeared to enhance the production of SSB. DNA damages induced by MMS should cause various genetic effects during the postmeiotic stages and maturation of spermatozoa through mechanisms not related to excision repair.