THE IMMATURE RAT UTERUS AS AN ASSAY END-POINT FOR GONADOTROPIC SUBSTANCES

Abstract

A comparison of the following gonadotropic end-points was made vaginal opening, vaginal, uterine, and ovarian weights. Suspensions made from 57 pooled whole pituitaries of mature [female] rats, castrated 20 days previously, were injected into 15 immature rats on each of 14 closely graded dose levels. Minimal doses producing uterine and vaginal weight increase were about 1/3 to 1/2 as large as the minimal dose causing vaginal opening, and only 1/8 as large as the minimal dose producing ovary weight increase. Vaginal opening was least dependable, while uterine weight was considered the most satisfactory end-point. Preliminary observations show that the ratio of uterine to ovarian units, and the shape of the uterine weight curve, differ according to the source of gonadotropic material.