Sex steroids modulate the synthesis and phosphorylation of proteins in thebrain cortex of aging mice

We have analysed the synthesis and phosphorylation of total cellular protei ns and their modulation by sex steroids (testosterone and 17 beta-estradiol ) in the brain cortex of adult (25-28 weeks) and old (54-58 weeks) male and female AKR mice. The level of (S-35) methionine incorporation in total pro teins is comparatively higher in males than females. It declines significan tly in older males but shows no difference with age in females. After gonad ectomy, the extent of (S-35) methionine incorporation decreases in adults b ut not in the old. The incorporation is induced remarkably by estradiol in males and by both sex steroids in females. Further analysis by fluorography shows several proteins, but only a few (66, 45 and 29 kDa) vary in levels significantly with age, sex and hormonal treatment. The data on phosphoryla tion of total cellular proteins by (P-32) orthophosphate incorporation exhi bit no age-dependent variation. However, it is reduced drastically by gonad ectomy in adults. After the addition of testosterone, the extent of phospho rylation is enhanced significantly in adults but remains the same in the ol d of both sexes. Estradiol also increases this modification remarkably in m ales of both ages and adult females, but shows no effect in old females. Th ese results suggest that both testosterone and estradiol modulate the synth esis and phosphorylation of brain cortex proteins in age- and sex-dependent manner. This leads to alterations in physiological activities of the anima l. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.