Regulatory changes in glucocorticoid receptors in the skeletal muscle of immature and mature male rats.
Specific binding of [3H]dexamethasone to cytosol and translocation of bound receptor complexes to purified nuclei were studied in the skeletal muscle of immature (3-week) and mature (26-week) Long-Evans male rats. A marked decrease (57%) in the specific binding sites with no apparent change in dissociation constant (Kd) was observed in the skeletal muscle of mature rats compared to immature. Heat activation (25 degrees C for 45 min) significantly enhances the nuclear binding of steroid-receptor complexes in the skeletal muscle of rats of both the ages at almost similar level. Cross-mixing experiments (i.e. binding of activated cytosol from mature rats to nuclei of immature and vice-versa) gave similar values. Interestingly, Ca2+-activated (0 degree C for 45 min with 20 mM Ca2+) nuclear translocation was significantly higher (27%) in the skeletal muscle of immature rats compared to mature. Our results indicate that glucocorticoid receptor level and some physicochemical properties change with age in the skeletal muscle of rats.
D000375:Aging; D000818:Animals; D001665:Binding Sites; D003907:Dexamethasone / Q000378:metabolism; D008297:Male; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
D011965:Receptors, Glucocorticoid; D003907:Dexamethasone