Estimation of Pituitary Gonadotropins in Human Plasma

Abstract

A rapid and simple method for estimation of gonadotropic activity in human plasma is described. The chemical procedure involves precipitation of plasma proteins with 5 ml of absolute ethanol per ml of plasma. The precipitate is then extracted twice with 2 ml of 10% ammonium acetate in 70% ethanol per ml of plasma used. Gonadotropic activity is measured utilizing the mouse uterine weight assay. The mean yield of solid material is about 8 % of the plasma solids, and the mean recovery of gonadotropic activity is 87 %. The purification is such that 20 ml equivalent of plasma can be administered to the test animal without toxic effects. One pool of postmenopausal plasma studied contained 17.880 μg equivalent for the 2nd International Reference Preparation of Human Menopausal Gonadotrophins (2nd IRP) per liter of plasma. Pools obtained from male subjects contained 1.200 μg equivalent of the 2nd IRP per liter. Pools from young female subjects obtained at random during the menstrual cycle contained 1.310 μg equivalent of the 2nd IRP. This method is suitable for the estimation of high gonadotropin titers, i.e., postmenopausal plasma. For low titers, i.e., plasma from male and female subjects in the reproductive years, only plasma pools can be employed.