[Inhibition of the uterine binding of estrogens by unsaturated fatty acids in immature female rats].

We demonstrate that the interactions between the uterine cytosol proteins of 24 day old Rats and estradiol-17 beta (E2) are significantly influenced by physiological concentrations of non esterified fatty acids (2. 10(-4)M). We show that the specific binding of the hormone to the 8S uterine receptor, is markedly inhibited (50-80%) by the unsaturated fatty acids.

alpha-Fetoprotein is not a component of the estradiol receptor of the rat uterus.

In high-salt medium, cytosol from immature rat uteri displays two main high-affinity estradiol-binding peaks after ultracentrifugation in a sucrose gradient. The two components are the estradiol receptor which has a sedimentation coefficient of 5.5 S, and the alpha-fetoprotein which sediments at 4.

[Characterization of the "4 S-trypsin" form of the cytosoluble estradiol receptor of calf uterus in a nondenaturing system].

The characterisation of the "4 S-trypsin" form of the estradiol-receptor from calf uterus cytosol was carried out by polyacrylamide gel electrophoresis under non-denaturing conditions. In a multiphasic buffer system (upper buffer Tris-glycine pH25degrees C = 8,6, lower buffer Tris HCl pH25degrees C = 7,4), three radioactive estradiol peaks were observed. The first was free estradiol, the second estradiol initially complexed with a macromolecule and dissociated during electrophoresis, and the third the hormone-receptor complex.

Affinity chromatography of the uterine estradiol receptor on estradiol-PAB-cellulose: an artefact.

Estradiol-PAB-cellulose, an easily prepared adsorbent, has been proposed to purify the uterine estradiol receptor according to the principle of biospecific affinity chromatography. It apparently removes all hormone binding sites when cytosol preparations are incubated with it. A systematic study of this adsorbent was undertaken, including the synthesis and testing of the radioactive material.