³H-Estradiol:<i>In Vitro</i>Binding to Macromolecules from the Rat Hypothalamus, Anterior Pituitary and Uterus

Abstract

The in vitro interaction of 3H-estradiol with macromolecules from various organs was studied. Tissues from ovariectomized rats were homogenized in Tris-HCl containing EDTA and radioactive estradiol mixed with the 100,000 × g supernatants. After incubation macromolecular bound radioactivity was separated by gel filtration. Higher concentrations of radioactive estradiol were found in the macromolecular fractions from the hypothalamus, anterior pituitary and uterus than from the cerebrum, cerebellum, heart or plasma. The binding molecules from the hypothalamus, anterior pituitary and uterus were found to have the following properties. Nonradioactive estradiol (10−7m) reduced binding, whereas progesterone or testosterone (10−5m) did not. Intravenous injection of nonradioactive estradiol decreased subsequent binding of 3H-estradiol in vitro. The binding molecules contain protein and appear to have sulfhydryl groups that influence the interaction with estradiol. (Endocrinology86: 1313, 1970)