Molecular Weight of Human Chorionic Gonadotropin as Estimated by Means of Radiation Inactivation of Biologic Activity

Abstract

The rate of radiation inactivation of human chorionic gonadotropic hormone and crude kaolin-acetone extracts of pregnancy urine caused by 2.0 Mev electrons has been studied. Four bio-assays have been used: ovarian hyperemia and uterus weight increase in intact, immature female rats; and prostate and testes weight increments in hypophysectomized male rats. The dose of radiation required to reduce activity to 37% (D37) was obtained by measurement of the slope of a graph of logarithm of percentage activity remaining plotted against radiation dose in rads. From these data estimations of molecular weight were made. The slopes, D37, and molecular weights were similar as measured by the 4 bio-assays for both the partially purified HCG and the pregnancy urine extracts. The average molecular weight was 30,500. Methods of application of radiation inactivation to hormonal materials are presented. The possible significance of these data is discussed.