The endocrine function of rat gonads with reduced number of germ cells following busulphan treatment

The endocrine function of rat gonads with an experimentally reduced number of germ cells was examined to analyse the effect of germ cells on the surrounding somatic endocrine cells. Pregnant Wistar rats received a single i.v. injection of 10 mg/kg B.W. of Busulphan on day 15 of gestation to prevent fetal primordial germ cells from starting mitotic division. The gonadal growth and the number of germ cells in Busulphan-treated rats (B-rats) were severely arrested. Almost a normal testicular structure was formed in the males, while few follicular structures were formed in the females, suggesting that the presence of oocytes in the fetal ovary is a prerequisite to the formation of the follicle. The meiotic division of spermatogonia in B-rats, which started on day 20 as in controls, stopped before the completion of spermatogenesis, and germ cells disappeared by day 50. The remaining germ cells and the associated follicles in female B-rats also disappeared by day 60 after repeating irregular estrous cycles for approximately 1 month. Thereafter the ovary consisted of fibroblasts and morphologically interstitial-like cells. Vaginal opening occurred in B-rats on day 28-30, a-week earlier than in controls. Changes in serum GTH after ovariectomy and the estradiol treatment suggested the maturation of the negative feedback sensitivity to estradiol in this period, and besides, earlier estradiol production with less dependency on gonadotropin. The vaginal epithelium of B-rats was cornified continuously after day 60. The ovarian cells in this period did not luteinize either morphologically or functionally in response to an ovulatory dose of hCG. During the same period, the conversion rate from progesterone to estradiol in ovarian homogenates of B-rats was considerably higher than those of controls at any stage of the estrous cycle. High content of estradiol was detected in the testes of B-rats at any age. In male B-rats, both LH and FSH levels in serum were higher than controls. The serum testosterone concentration in B-rats was lower than the normal, while the testicular testosterone content was greater. In conclusion, with a decreased number of germ cells, the rat gonads of both sexes secrete estradiol very efficiently.