Progesterone in the uterus. IV. Dependence of the in vitro progesterone metabolism in the rat uterus on the progesterone concentration.

After incubation of uterine segments of normal rats with various 3H-progesterone concentrations in nutrient medium, different patterns of radioactive steroids were obtained in uterine tissue. Using hormone concentrations of less than 5 X 10(-7)M progesterone metabolites could not be detected in the tissue. A series of metabolites appeared with progesterone concentrations of 10(-6)M and higher. Six radiometabolites were identified and two were characterized.