ASSESSMENT OF THE FUNCTION OF THE SEMINIFEROUS TUBULES AND INTERSTITIUM OF THE RAT TESTIS FOLLOWING LIGATION OF THE VASA-EFFERENTIA

The effects of bilateral ligation of the vasa efferentia on testis function were studied in sexually mature rats. Three weeks after this operation, the germinal epithelium was reduced mainly to spermatogonia and Sertoli cells which contained large amounts of lipid rich in unsaturated sterols. These degenerative changes were not modified by the administration of large doses of androgen and the sterilizing effects of this operation are not readily attributed to a lack of tropic stimulation. Seminiferous tubules and interstitial tissue were isolated by microdissection from a constant portion of control and ligated testis, incubated with equimolar amounts of [3H]pregnenolone and [14C]progesterone for 2 h and the products identified and estimated. The total metabolism of [14C]progesterone by the tubules was the same in the 2 groups. However, there was an increase in the yield of 20α-dihydroprogesterone and a corresponding decrease in the formation of 3β-hydroxy-5α-pregnan-20-one from [14C]progesterone in incubations with tubules from ligated testes when compared with the control values. [3H]pregnenolone was poorly metabolized by tubules from both control and experimental animals and no significant differences were found in the yields of metabolites from this substrate. The Leydig cells in the ligated testis retained the cytological features and low lipid content characteristic of the functional cell. The amount of interstitium recovered from the testis by microdissection was the same in both experimental and control animals and the ability of this tissue to produce androgens from [3H]pregnenolone and [14C]progesterone in vitro and to maintain the accessory sex organs was undiminished. The present data confirm that the seminiferous tubules exhibit a distinct pattern of lipid and progesterone metabolism which is governed by the level of spermatogenic activity and, in the regressed testis, is modified independently of any change in Leydig cell function.