Maintenance of rate testis fluid testosterone and dihydrotestosterone levels by pregnenolone and other C21 steroids in hypophysectomized rats.

This study was undertaken to determine whether maintenance of spermatogenesis in hypophysectomized rats by pregnenolone and other C21 steroids may be due to in vivo conversion of these compounds to androgens. Hypophysectomized rats were treated sc with 2 mg of pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone or testosterone propionate in 0.2 ml sesame oil daily for 14 days beginning 2 days after hypophysectomy. Rete testis fluid (RTF), peripheral blood, and testicular venous blood were collected on the day of the last injection. Testosterone (T) and dihydrotestosterone (DHT) were measured by radioimmunoassay after chromatographic separation. Results demonstrate that T and DHT could be found in the RTF of C21 steroid-treated hypophysectomized rats at levels similar to those seen in the intact rat. Results imply that the maintenance of spermatogenesis by C21 steroids is probably due to the conversion of these compounds to T in the testis. Relatively little T was released from the testis into the peripheral circulation of these rats since T levels in testicular venous plasma were low and peripheral plasma T levels were not distinguishable from those seen in untreated hypophysectomized rats. Histological examination of the testes of C21 steroid-treated hypophysectomized rats showed nearly quantitative maintence of spermatogenesis and atrophy of Leydig cells. These findings suggest that most of the conversion of C21 steroids to androgens occurred in the seminiferous tubules.