title: Prevention of the abortifacient action of antiprogesterone serum by progesterone.
abstract: Earlier studies1-4 showed that when rats of 10 days' gestation are passively immunized with antiprogesterone (A-P) globulins the biologically available progesterone (P) unbound by A-P (Pu) not only falls precipitously but also remains low for days, despite the rapid clearance of A-P. This finding suggested that the effective reduction of Pu affects P synthesis, probably through action on the fetoplacental unit. If so, pregnancy should be protected from the effect of A-P by P treatment to prevent the reduction of Pu. The present studies demonstrated that if P treatment was delayed for six hours after the administration of A-P, Pu did not return to physiologic levels, and pregnancy did not continue. However, if P was given three hours after A-P, at the same time, or three hours before A-P, the reduction of Pu was short-lived or prevented, and thus pregnancy was protected.
mesh_terms: D000019:Abortifacient Agents / Q000494:pharmacology*; D000818:Animals; D005260:Female; D007106:Immune Sera; D011247:Pregnancy / Q000187:drug effects; D011374:Progesterone / Q000096:biosynthesis / Q000276:immunology* / Q000378:metabolism / Q000494:pharmacology; D051381:Rats; D012712:Serum Globulins / Q000037:antagonists & inhibitors; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D000019:Abortifacient Agents; D007106:Immune Sera; D012712:Serum Globulins; D012965:Sodium Chloride; D011374:Progesterone