PROLONGED ACTIVITY IN VIVO OF RABBIT ANTISERA TO PLACENTAL GONADOTROPHINS

Abstract

SUMMARY Antisera were raised to pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (HCG) in male rabbits. The biological potencies of the antisera, A-PMSG and A-HCG, were determined against homologous antigens PMSG and HCG, using the mouse uterus test in immature mice. A single injection of A-PMSG was shown to inhibit the response to PMSG when injected as late as 21 days after the antiserum. The duration of inhibition was shown to depend on the dose of antiserum injected. These results were confirmed in hypophysectomized mice. A-HCG was shown to cause similar prolonged inhibition of the response to HCG in intact mice. The results suggest that A-PMSG and A-HCG persist in the circulation of the mouse for periods of time expected on the basis of the known half-life of rabbit γ-globulin (5 days).