Studies on the structure and function of the mammalian testis IV. Steroid metabolism in vitro by isolated interstitium and seminiferous tubules of rat testis after heat sterilization

A study has been carried out on the metabolism of [7α-3H] pregnenolone and [4-14C] progesterone by the interstitium and seminiferous tubules isolated from the testes of normal rats and those in which the germ cells were destroyed by exposing the scrotum to a temperature of 43°C for 30 min. No difference was found between the ability of the interstitium of the experimentally treated rats to metabolize the radioactive substrates as compared with that of normal animals. Similarly, no change was found in various androgen dependent features (mass of accessory sex organs and fructose levels of the coagulating glands) in the experimentally treated rats as compared with the controls. In the seminiferous tubules of the heat-treated animals the metabolism of progesterone in vitro was significantly increased as compared with that found in the tubules of normal rats in vitro due mainly to a much greater production of 20α-hydroxypregn-4-en-3-one. There was no significant difference in the relative proportions of 17α-hydroxyprogesterone, androstenedione and testosterone obtained from the incubations of heat-treated tubules as compared with the normal (control) tissue. It is concluded that within the seminiferous tubules, the Sertoli cells are the principal site of the enzymes responsible for the metabolism of pregnenolone and progesterone in vitro to androgens and to 20α-hydroxypregn-4-en-3-one. The possible biological significance of the enhanced production of 20α-hydroxypregn-4-en-3-one is discussed.