Metabolism of progesterone in the canine feto-placental unit.

Progesterone (P), a major hormone of pregnancy, was selected for study under the conditions of an intact utero-placental-fetal unit. A preparation of the canine gravid uterus, near term, is described and shown to permit observation of the metabolic relationships of the steroid hormone P between maternal and fetal organisms. [1,2-3H] P or [7 alpha-3H]P was injected into pups, while [4-14C]P was injected into the uterine circulation. Perfusion was continued for 1 hr with excellent survival of the pups. Identified metabolites in the fetal and maternal tissues suggest a metabolic pool that is shared throughout the unit.