ETHYL METHANESULFONATE INDUCED CHANGES IN THE DIFFERENTIATION, STRUCTURE AND FUNCTIONS OF SPERMATOZOA OF THE HOUSE RAT, RATTUS-RATTUS L

Intraperitoneal administration of 500 mg/kg and 625 mg/kg doses of the germ cell mutagen, ethyl methanesulphonate (EMS) in 5 consecutive day s to the house rat, Rattus rattus caused a dose-dependent reduction in its body weight, cauda epididymides weight, concentration, motility a nd percentage of live spermatozoa with simultaneous increase in the pe rcentage of their abnormal forms. Compared to 0.65% spermatozoa with a bnormal heads in the cauda epididymidis of untreated control rats, 24. 86% and 65.72% such spermatozoa were observed in rats on day 14 post t reatment with 500 mg/kg and 625 mg/kg doses of EMS respectively. On da y 28 post treatment corresponding values for abnormal spermatozoa were 16.21% and 14.32%. Similarly, spermatozoa with abnormal flagella incr eased from 0.78% in control rats to 9.25% and 5.75% on day 14 post tre atment of 500 and 625 mg/kg doses of EMS respectively and declined to 2.91% and 2.40% on day 28 post treatment. Abnormality in the sperm hea d was mainly due to acrosomelessness and in the flagellum due to bendi ng at proximal region. However, the main effect of EMS was the develop ment of spermatozoa without or deformed acrosomes which may impair the fertility of rats. Analysis of various stages of differentiation of s permatozoa in the testis revealed that population of preleptotene and pachytene spermatocytes and of round spermatids showed a gradual decli ne which became significantly less than controls on day 28 of EMS trea tment. Occurrence of abnormal heads of testicular spermatids indicated that the sperm head abnormalities originated in the testis during lat e spermiogenesis.