48-hour assay test for equine gonadotropin with results expressed in international units

Abstract

Since earlier work has indicated that only one gonadotropin exists in pregnant mare serum, a method of assay based solely upon a quantitative ovarian response has been devised. The ovarian weight response to equine gonadotropin at varying dosage levels was determined at 24, 48, 72, 96, and 120 hours after a single injection. The differences between mean ovarian weights, dependent upon dosage, were as significant at 48 hours as they were at longer intervals. Our rat unit, used for several years, is approximately equivalent to the International Unit. Contrary to the findings of others using human urine gonadotropins, it appears that the ovarian response to equine gonadotropin is more reliable than the uterine response and the ovarian weight method has the added advantage of being a direct response. Using values obtained by use of the International Standard, a regression line that may serve for determining potency of equine gonadotropins by interpolation has been calculated. © 1941 by The Endocrine Society.