Inactivation of hepatic glucocorticoid receptors by heparin.
Heparin dramatically enhanced the rate of unbound glucocorticoid receptor inactivation in vitro in a concentration, time and temperature-dependent manner. Control specific binding decreased only about 25% after incubation for 6 h at 4 degrees C. However in the presence of heparin (40 micrograms per ml cytosol) receptor binding decreased about 75%. At 25 degrees C liver receptor specific binding was found to have a half-life of about 60 min in control cytosol. However, in the presence of heparin (40 micrograms per ml cytosol) the glucocorticoid receptor had a half-life of only 15 min at 25 degrees C. Interestingly, 10 mM molybdate (with or without 5 mM dithiothreitol) greatly inhibited heparin-dependent receptor inactivation at 4 degrees C. Dithiothreitol (alone) significantly stabilized receptor binding in control samples at 4 degrees C, but provided no protection from heparin-dependent receptor inactivation. Heparin had no apparent inactivating effect on prebound glucocorticoid receptor complexes at 4 degrees C. Interestingly however, heparin altered the sedimentation coefficient of prebound hepatic glucocorticoid-receptor complexes in low salt gradients from 7-8 S to about 3-4 S. When molybdate plus dithiothreitol were added with heparin, the sedimentation coefficient was found to be approx. 6-7 S. These results demonstrate that heparin, which is often used pharmacologically and which occurs naturally in animal tissues, has significant effects on liver glucocorticoid receptors in vitro.
D000818:Animals; D003600:Cytosol / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004355:Drug Stability; D006493:Heparin / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008982:Molybdenum / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000187:drug effects*; D011987:Receptors, Steroid / Q000187:drug effects*; D013696:Temperature; D013997:Time Factors; D014221:Triamcinolone / Q000494:pharmacology
D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D014221:Triamcinolone; D008982:Molybdenum; D006493:Heparin; C024687:sodium molybdate(VI); D004229:Dithiothreitol