Adenohypophyseal and Serum Gonadotrophins in Male Rats Treated Neonatally with Estradiol Benzoate

Abstract

This study investigated the effect of 100 [mu]g of estradiol benzoate injected during the 5th day of life on pituitary and serum concentrations of gonadotrophins in intact and orchidectomized male rats. The ovarian ascorbic acid depletion method of Parlow was used for the assay of pituitary and serum luteinizing hormone (LH). The adenohypophyseal and serum concentration of follicle stimulating hormone (FSH) was determined by means of the augmentation method of Steelman and Pohley. Neonatal administration of estradiol benzoate to male rats resulted in animals with significantly smaller testes, ventral prostate and seminal vesicles. No differences in pituitary LH concentration were observed between estrogen-treated and non-injected controls of 60 days of age, but 180-day-old estrogen-injected males showed a significantly higher LH concentration value than their controls. Determination of pituitary FSH concentrations showed no significant differences between estrogen-treated and control animals of 60 and 180 days of age. Castration of 4-month-old estradiol-treated male rats resulted in a marked increase in adenohypophyseal LH concentration, no changes in pituitary FSH, and a rise in the blood serum concentration of both gonadotrophins to detectable levels. These changes observed 2 months following orchidectomy did not differ from the response of non-injected control rats. The contrast between the marked disturbances in gonadal function observed in estradiol-treated rats and the relatively normal pituitary FSH and LH concentration levels can best be explained by postulating the existence of abnormalities in both the synthesis and the release of gonadotrophins. The results observed following orchidectomy indicate that the estradiol-treated rats are capable of normal increases in synthesis and release of FSH and LH in response to a drop in testicular hormone levels and suggest that this aspect of the feedback mechanism has not been impaired by the effect of the neonatal hormone treatment.