Alteration of hepatic glucocorticoid receptor stability and nuclear binding in vitro by citrate.
Citrate greatly stabilized rat hepatic unbound glucocorticoid receptors in cell-free conditions at 4 degrees C with optimal effectiveness at 5-15 mM. Control receptors were inactivated at 4 degrees C with a half-life of less than 12 h. However, in the presence of 10 mM-citrate, unbound receptors were almost completely stabilized for 48 h at 4 degrees C. Citrate at a concentration of 1-2 mM yielded half-maximal stabilization. The stabilizing effect of citrate was rather specific, as succinate, alpha-oxoglutarate, oxaloacetate, malate and pyruvate had no apparent stabilizing action. Citrate stabilized receptors over a wide range of H+ concentrations, with complete protection between pH 6.5 and 8.5. In addition, citrate appeared to have a significant effect on glucocorticoid-receptor complex activation into a nuclear binding form. Thus 5-10 mM-citrate enhanced nuclear binding, with optimal activation achieved at 10 mM concentration. As analysed by sucrose-density-gradient centrifugation and DEAE-cellulose chromatography, no apparent change was observed in the physical characteristics of the glucocorticoid receptor in the presence of citrate.
D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002951:Citrates / Q000494:pharmacology*; D019343:Citric Acid; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000187:drug effects / Q000378:metabolism*; D011987:Receptors, Steroid / Q000378:metabolism*
D002951:Citrates; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D019343:Citric Acid