Maintenance of Rete 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 C₂₁steroid s may be due to in vivo conversion of these compounds to androgens. Hypophy-sectomized rats were treated SC with 2 mg of pregnenolone, 17–hydroxypregnenolone, proges-terone, 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 in ection. Testosterone (T) and dihydrotestosterone (DHT) were measured by radioimmunoassay after chromatographic separation. Results demonstrate that T and DHT could befound 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 C₂₁steroids 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 levelsin testicular venous plasma were low and peripheral plasma T levels were not distinguishable fromthose seen in untreated hypophysectomized rats. Histological examination of the testes of C₂₁steroid-treate d hypophysectomized rats showed nearly quantitative maintenance of spermatogenesis and atrophy of Leydig cells. These findings suggest that most of the conversion of C₂₁steroid s to androgens occurred i n the seminiferous tubules. (Endocrinology96:1396, 1975)