THE USE OF PARABIOTIC MICE FOR THE STUDY OF PITUITARY GONADOTROPHIN HYPERSECRETION AND ITS INHIBITION BY STEROIDS1

Abstract

Comparative observations on a total of 551 pairs of parabiotic rats and over 1000 pairs of parabiotic mice suggest the usefulness of parabiotic mice for the study of gonadotrophin hypersecretion and its regulation by certain steroids. The advantage of the use of parabiotic mice for this study resides in the relative ease and speed of parabiotic operation, no need of littermates as long as inbred mice are used and low mortality of parabionts. The pituitary-gonad relations observed in parabiotic mice are quite similar to those in parabiotic rats. Namely, the gonadotrophic potency of the male pituitary is larger than that of the female either in the normal or in the castrated condition, and greater amount of sexagen is required to inhibit gonadotrophin hypersecretion of the male pituitary. Estradiol is more potent than testosterone propionate in its anti-gonadotrophic activity. A lesser amount of steroid can regulate the secretion of pituitary gonadotrophin than that which stimulates the peripheral targets, especially in the female mice.