Hypothalamo-hypophyseal-gonadal system in male rats and guinea pigs treated with the antiandrogen 4-nitro-3-trifluoromethylisobutyranilide.

Influence of the competitive testosterone antagonist 4-nitro-3-trifluoromethylisobutyranilide (NFBA) on the hypothalamo-hypophyseal-gonadal system in male Wistar rats and guinea pigs was studied. NFBA as well as nonlabelled testosterone diminished 3H-testosterone uptake in hypothalamus and hypophysis of castrated animals. Increase of plasma testosterone level was obtained after the antiandrogen treatment in a dose of 10 or 25 mg/kg per os during 3, 10 and 48 days. Maximal level of the hormone was noticed on the 10th day. The contents of 17-ketosteroids in testes had not changed, but the testosterone content and steroid-delta5-3beta-ol-dehydrogenase activity were high during the treatment period. After 10 days of NFBA administration increased plasma LH level was found. Increase in size and number of gonadotropocytes was revealed by histological and histochemical methods as well as Leydig cell hypertrophy. High plasma testosterone level and Leydig cell activation were obtained in guinea pigs as a result of NFBA subcutaneous injections in a dose of 10 mg/kg during 30 days. The suggestion is made that prolonged NFBA treatment produces changes in the testosterone metabolism. Short-term administration of NFBA may be used for the estimation of the hypothalamo-hypophyseal functional abilities.