THE PITUITARY-GONAD RESPONSE OF GENETICALLY OBESE MICE IN PARABIOSIS WITH THIN AND OBESE SIBLINGS1

Abstract

Gonadectomized mice that were either obese or nonobese, male or female were parabiosed to either obese or nonobese immature female siblings. The experiment was designed (a) to compare the production of gonadotrophin by the pituitaries of the obese and non-obese gonadectomized animals and (b) to compare the relative responses of the reproductive systems of the obese and nonobese assay females to the gonadotrophin produced by the pituitary of the castrated partner. Results showed that, although the pituitaries of the gonadectomized obese mice of both sexes as well as those of the nonobese mice produced excess gonadotrophin, the obese animals elicited less ovarian hypertrophy in the assay female than did nonobese mice. Also, female animals elicited less response than males. The reproductive systems of the female obese and nonobese mice responded similarly to the excess gonadotrophin. It is concluded that, while the pituitaries of obese mice are competent to produce more gonadotrophin than they normally do, under the conditions of this experiment the pituitaries in obese mice were less competent than those in nonobese mice.