PITUITARY CONTROL OF THE TESTIS OF THE HYPOPHYSECTOMIZED RAT1

Abstract

The action of each of the purified pituitary hormones has been assessed in maintenance and repair of the reproductive system of the hypophysectomized 40-day male rat. When injections of interstitial cell stimulating hormone (ICSH) were begun immediately after hypophysectomy, the testicular weight and physiological status of tubules and Leydig cells were maintained and advanced. Testicular epithelium was extremely sensitive to low doses of ICSH and sperm were elaborated. Even at high doses of ICSH, testicular and accessory organ weights were not, however, completely normal for the chronological age. Follicle stimulating hormone (FSH), injected at doses which did not show contamination with ICSH, had only slight effects on testicular weight and development; only the highest levels of FSH injected caused barely perceptible stimulation of the accessory organs. However, low doses of FSH injected with ICSH increased testicular size and development. Doses of lactogenic and growth hormones, having no effect on the reproductive system alone, increased the response to ICSH and also further augmented the response to ICSH with FSH. A dose-response relationship was not demonstrated with increasing doses of either growth or lactogenic hormone. Other anterior pituitary hormones, thyrotrophic and adrenocorticotrophic, had no influence on the reproductive system given alone or with the gonadotrophins. It should be emphasized that no hormone maintained the testicular tubules of the Tiypophysectomized male rat unless ICSH was present. In repair of the testis after post-hypophysectomy regression, ICSH did not act as a complete gonadotrophin. Though it repaired the Leydig cells it caused no more than slight repair of the testicular tubules even at high doses. FSH alone was without effect in repair, but was extremely important in cooperative action with ICSH. The combination of ICSH with FSH induced tubular differentiation, sperm appearing in some instances, and augmentation of growth of accessory organs was definite. Addition of either growth or lactogenic hormone to the combination of ICSH with FSH increased the degree of stimulation; simultaneous injection of all four hormones was even more effective, and was the only treatment using purified hormones in which sperm were formed in all animals. (Extracts of rat pituitaries caused similar development after post-hypophysectomy regression.) In repair, as in maintenance of the testis, no combination of pituitary hormones was effective unless ICSH was present.