title: The aging Leydig cell: VII. Cytoplasmic estradiol receptors.
abstract: Plasma estradiol and cytosolic estradiol receptor levels of testes were determined in a group of young (2-3 months) and old (24 months) Sprague-Dawley rats. Estradiol binding sites for the young rats averaged 5.6 +/- 0.3 fmol/mg protein (x +/- SE, n=12), which was comparable to that of the old rats, 5.7 +/- 0.3 fmol/mg protein (n=12). Using Scatchard analyses, the association constants at equilibrium of estradiol receptor binding of the old and young rats were the same, 6.1 x 10 10 M-1. Plasma estradiol levels were also similar in both groups-19.6 +/- 2.8 pg/ml (n=14) for the young and 19.2 +/- 2.6 pg/ml (n=10) for the old rats. Our results suggest that impaired testosterone biosynthesis in old rats was not due to elevated plasma estradiol levels or to differences in testicular estradiol receptor content.
mesh_terms: D000375:Aging; D000818:Animals; D001667:Binding, Competitive; D003600:Cytosol / Q000378:metabolism; D004958:Estradiol / Q000097:blood / Q000378:metabolism*; D007700:Kinetics; D007985:Leydig Cells / Q000378:metabolism*; D008297:Male; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D011959:Receptors, Estradiol; D011960:Receptors, Estrogen / Q000378:metabolism*; D013737:Testis / Q000254:growth & development*
chemical_list: D011959:Receptors, Estradiol; D011960:Receptors, Estrogen; D004958:Estradiol