Differential response of testis and serum gonadotropins to testosterone in rats treated with a gonadotropin releasing hormone antagonist or estradiol 17 beta.

Adult rats treated with a GnRH antagonist (Ac D2Nal1, D4Cl Phe2, DTrp3, DArg6, DAla10 GnRH; code: 103-289-10, National Institutes of Health, USA) for 5 weeks (250 micrograms/kg b.w) showed multiple degrees of impairment and atrophy of the genital organs concomitant with decreased serum levels of testosterone, LH and FSH. Inhibition of spermatogenesis was characterized by germ cell degeneration and overall decline in different cell numbers and in particular, spermatids of any kind were completely absent. Testosterone supplementation (60 micrograms/rat/day, sc) to GnRH antagonist treated rats, for the same period, significantly elevated the weights of the sex organs, and the serum levels of hormones. Spermatogenesis was improved both qualitatively and quantitatively; albeit failed to be restored back to control levels. Treatment with estradiol 17 beta (1 microgram/rat/day) for 5 weeks had insignificant effect on spermatogenesis but the weights of the genital organs (seminal vesicles by 19% and ventral prostate by 40%) and the levels of serum hormones (LH by 24%, FSH 22% and testosterone by 25%) were otherwise reduced. Administration of testosterone either alone or in combination with estradiol 17 beta had only a marginal effect on spermatogenesis or on other reproductive parameters. The results indicate a positive shift in the response of the testis and serum levels of gonadotropins to testosterone supplementation in rats treated with either GnRH antagonist or estradiol 17 beta.