Diethylstilbestrol-treated adult rats with altered epididymal sperm numbers and sperm motility parameters, but without alterations in sperm production and sperm morphology

In this study, we characterized estrogenic effects of diethylstilbestrol (D ES) on reproductive parameters in male rats to identify a minimal dose leve l that alters epididymal and sperm functions but has little or no effect on sperm production and/ or spermatogenesis. Adult rats (five animals/group) received s.c. injections of 0.2 ml of corn oil containing DES at a rate of 1.0 mg, 200 mug, 40 mug, 8 mug, 1.6 mug, or 320 ng rat(-1) day(-1) for 12 d ays. The control group received corn oil only. DES effects were similar in the 8-mug group and higher dose groups and included significant (P less tha n or equal to 0.05) reductions in 1) absolute and relative weights of the h ead and body of the epididymis (EP), tail of the EP, and seminal vesicle, 2 ) numbers of sperm in both regions of the EP, and 3) motility characteristi cs in sperm collected from the tail of the EP. Conversely, no significant c hanges were observed in relative testis weight, daily sperm production, spe rmatogenesis, seminiferous epithelial height in stage VII, and sperm morpho logy. All of the above parameters in the 1.6-mug group (except seminal vesi cle weight) and 320-ng group were comparable to those of controls. Plasma t estosterone (T) level was reduced to an almost undetectable level in the gr eater than or equal to8-mug groups and to a very low level in the 1.6-mug g roup (0.35 vs. 2.36 ng/ml in controls or 320-ng group), but LH level was un altered. In a parallel fertility study, males received DES at a rate of 40, 8, or 1.6 mug rat(-1) day(-1) for 12 days prior to and 12 days during coha bitation (1:1) with untreated females. Of the 15 females cohabited with tre ated males (5 females/dose), none in the 40-mug and 8-mug groups and 1 in t he 1.6-mug group formed a copulatory plug and delivered 8 pups, in contrast to 5/5 copulatory plugs and 13-15 pups/litter in the controls. DES at a ra te of 8 mug rat(-1) day(-1) for 12 days reduced EP weights, sperm numbers i n the EP, and sperm motility patterns but caused minimal to no alterations in daily sperm production, spermatogenesis, or sperm morphology. Factors ot her than T, or in addition to lower T, may be responsible for DES-induced r eproductive disorders (despite lower T, sperm contents and sperm motility p atterns in the EP were normal in the 1.6-mug group). Deficits in EP sperm f unctions and/or sexual behavior las evident from absence of copulatory plug s) probably accounted for reduced fertility in treated males.