Age-dependent activation of glucocorticoid receptors in the liver of male rats.
The binding of hepatic [3H] dexamethasone-receptor complexes to DNA-cellulose and purified nuclei was studied in the immature (3-week) and mature (26-week) Long-Evans male rats to determine the age-associated 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 binding of [3H] dexamethasone-receptor complexes to DNA-cellulose and purified nuclei at both the ages, with a greater magnitude in mature rats. Cross-mixing experiments (i.e. binding of activated cytosol from mature rats to nuclei of immature and vice-versa) show receptor specificity. Ca2+ activation (20mM Ca2+ for 45 min at 0 degrees C) also enhances the nuclear and DNA-cellulose binding at both the ages but to a similar extent. 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 these phases of the life span. The observed changes may lead to functional alterations in the tissue response as a function of age.
Sharma
R
R
Department of Physiology-Anatomy, University of California, Berkeley 94720.
Timiras
P S
PS
D000375:Aging; D000818:Animals; D001711:Biotransformation; D002482:Cellulose / Q000031:analogs & derivatives / Q000378:metabolism; D004247:DNA / Q000031:analogs & derivatives / Q000378:metabolism; D006358:Hot Temperature; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*
C033190:DNA-cellulose; D011965:Receptors, Glucocorticoid; C028697:dexamethasone receptor; D002482:Cellulose; D004247:DNA