Progesterone in the uterus. V. Correlation of the in vitro progesterone metabolism with the progesterone binding in rat uterus.

Incubations of rat uterine segments with varying 3H-progesterone concentrations were performed to study the hormone uptake by the tissue. The radioactivity of the uterus and the nutrient medium were plotted in form of a SCATCHARD plot. Additionally, the binding capacity of the uterine cytosol was measured. In both systems, the hormone was found to be associated with two components which differ from each other in their association constants. The progesterone metabolism occuring at a hormone concentration of 10(-6)M and more in the incubation medium is discussed with respect to the affinity and the capacity of the hormone binding components.