In vivo uterine metabolism of progesterone and 5 alpha-pregnane-3,20-dione during the synthesis and release of uteroglobin in ovariectomized, steroid-treated rabbits.

Abstract

The metabolic clearance rate (MCR) and uterine metabolism of progesterone (P) and 5apregnane- 3,20-dione (5α-DHP) during the synthesis of uteroglobin in the rabbit uterus have been studied. Oophorectomized rabbits with the uteri ligated received daily im injections of vehicle (C), P (0.5 mg/kg BW), estradiol (E2; 2 μg/kg BW), or P plus E2 for 5 days. The MCR of [MC]P and 5α-[3H]DHP, the uterine extraction of P and 5α-DHP, and the uterine concentration of P and 5α-DHP were measured. There were no differences of MCR between groups. The blood MCR of P was 235 ± 10 (SE) liters/day and of 5α-DHP was 452 ± 18 (SE) liters/day. The ratio of the concentration of [14C]P in uterine tissue to arterial blood [MC]P concentration was influenced by the prior administration of steroids (E2 > C = P + E2 > P). A significant portion of the uterine tissue 14C was present specifically as [MC]P; (35 ± 4% (SE) in P-treated animals; 53 ± 4% (SE) in P + E2-treated animals; 50 ± 10% (SE) in C-treated animals; and 65 ± 7% (SE) in E2...