ENHANCEMENT OF PROGESTERONE-RECEPTOR BINDINGS BY ESTRADIOL IN PITUITARY-CELLS OF THE HEN

Isolated cells from pituitaries of nonlaying hens were incubated in vitro with and without estradiol-17-beta (E2), and the amount of progesterone receptor binding in the cytosolic fraction of the cells was measured by an exchange assay. When the cells were incubated with 1.0 ng E2 for 1, 2, or 4 h, the progesterone receptor bindings were increased. The bindings were not increased when incubated together with cycloheximide, actinomycin-D, or alpha-amanitin. The results suggested that the cytosolic progesterone receptor binding of pituitary cells was enhanced by the action of estrogen through a protein-synthesizing pathway.