Age-dependent activation of glucocorticoid receptors in the cerebral hemispheres of male rats.

The binding of [3H]dexamethasone-receptor complexes to purified nuclei was studied in the cerebral hemispheres of immature (3-week-old) and mature (26-week-old) Long-Evans male rats to determine the age-related changes, if any, in the physicochemical properties of glucocorticoid receptors. Our data show that heat activation (for 45 min at 25 degrees C) significantly enhances the nuclear binding of [3H]dexamethasone-receptor complexes in rats of both ages, with a greater magnitude in immature rats. Ca2+ activation (20 mM Ca2+ for 45 min at 0 degree C) also enhances the nuclear binding of bound receptor complexes but to a similar extent at both ages. These findings indicate that some of the physicochemical properties (e.g. heat activation) of glucocorticoid receptor change, while others (e.g. Ca2+ activation) remain unchanged at different phases of the lifespan.