The metabolic clearance rate, the brain extraction and distribution and the uterine extraction and retention of progesterone and R 5020 in estrogen-treated ovariectomized rabbits

Abstract

The metabolic clearance rate (MCR), uterine extraction, uterine retention and brain distribution of the synthetic progestin R 5020 and progesterone were studied in estrogen-treated ovariectomized rabbits. The MCR of R 5020 was 163+/-15 (SE) 1/day and was lower than that of progesterone. The uterine extraction of R 5020 (51.4+/-3.9 (SE)%) was greater than that of progesterone (33.7+/-7.7%) as was the uterine tissue:arterial blood ratio (28.1+/-4 vs. 7.3). The brain and pituitary retention and distribution of R 5020 and progesterone were the same and provided no evidence for a selective accumulation of a progestin in the pituitary or hypothalamus.