INHIBITION OF GONADOTROPIC ACTIVITY BY SEX HORMONES IN PARABIOTIC RATS

Abstract

There seems to be no doubt that castration in the rat results in an increase in the gonad-stimulating capacity of the hypophysis, and it is also generally accepted that estrogenic substances depress the gonadotropic power of the pituitary (1). Moore and Price have shown that bull testis extracts (2) and androsterone (3) injected into young male rats cause testicular damage. They attributed this injurious effect to a lowering of pituitary gonad-stimulating hormone, an idea supported by the fact that implantation studies showed the pituitaries of androsterone-injected rats to be reduced in gonadotropic potency. Of special interest are recent reports (4, 5) that ovarian weights in immature parabiotic rats could be used as a quantitative measure of hypophyseal gonadotropic secretion of castrated parabionts which were untreated or treated with estrone or androgenic substances. Our own observation (6, 7) on paraboitic rats suggested the possibility that the testicular response of hypophysectomized rats might serve as a qualitative indicator of the hypophyseal gonadokinetic activity of a castrated parabiont.