Detection of corticosteroid type I binding sites in heart.
Both high affinity (type I) and low affinity (type II) corticosteroid binding sites are detected in cytosolic extracts of atrial and ventricular tissue when [3H]aldosterone is used as the ligand. In the presence of RU-28362, which blocks binding of [3H]hormone to the low affinity type II sites, [3H]aldosterone binds to a single class of high affinity sites. The apparent Kd for binding of the hormone to the type I sites was 1.0 nM in atrial cytosol and 0.75 nM in ventricular cytosol. The concentration of type I sites in atrial (12 fmol/mg protein) and ventricular cytosols (11 fmol/mg protein) is comparable to reported values in renal (17-31 fmol/mg protein) cytosol. Activation of the type I hormone-receptor complexes to the DNA-binding form was examined using chromatography on DEAE-Sephadex anion-exchange resin. The unactivated hormone-receptor complex elutes at a concentration of 400 mM KCl. Following heat treatment (25 degrees C, 30 min) the [3H]aldosterone-receptor complex is transformed to a low salt eluting (200 mM KCl), DNA-binding form. Activation is blocked by inclusion of 10 mM sodium molybdate during heat treatment.
Barnett
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CA
Department of Biology, San Diego State University, CA 92182-0057.
Pritchett
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EL
D000305:Adrenal Cortex Hormones / Q000378:metabolism*; D000450:Aldosterone / Q000378:metabolism*; D000732:Androstanols / Q000494:pharmacology; D000818:Animals; D001665:Binding Sites; D003600:Cytosol / Q000032:analysis / Q000378:metabolism; D008297:Male; D009206:Myocardium / Q000032:analysis* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000032:analysis* / Q000378:metabolism; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid / Q000032:analysis* / Q000378:metabolism
D000305:Adrenal Cortex Hormones; D000732:Androstanols; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; C049154:11,17-dihydroxy-6-methyl-17-(1-propynyl)androsta-1,4,6-triene-3-one