Correlation between activity of antioxidant enzymes and circadian rhythms of corticosteroids in Macaca mulatta monkeys of different age.

Young rhesus monkey females (Macaca mulatta) demonstrate the well-defined circadian rhythm in activity of erythrocyte SOD with maximum at 10.00 h and minimum at 22.00 h. However, neither GSH-Px nor GR demonstrated any significant circadian changes, contrastingly to SOD. The diurnal changes in the SOD activity tightly correlate with the diurnal changes in the levels of cortisol and DHEAS in the animals' blood plasma. With aging, these circadian rhythms of SOD, cortisol and DHEAS are smoothed out although the correlation between the diurnal changes in cortisol and SOD still maintains even for old animals. These results suggest that corticosteroids play an essential role in regulation of the SOD activity and that the reliability of the hormonal regulation decreases with aging.

Circadian and age-related changes in stress responsiveness of the adrenal cortex and erythrocyte antioxidant enzymes in female rhesus monkeys.

BACKGROUND: The objective of this study was to evaluate the role of the adrenal cortex in the regulation of antioxidant enzyme defense and to characterize this regulation in different age periods. METHODS: Five young and five old female rhesus monkeys were subjected to 2 hours squeeze cage restraint stress at 0900 or 1500 hours. Plasma levels of corticosteroids and activities of erythrocyte antioxidant enzymes were measured before the stress and 30, 60, 120, 240 minutes after beginning of the stress. RESULTS: Young monkeys showed a circadian rhythm in stress responsiveness as measured by corticosteroids and glutathione reductase. The rhythm was attenuated in old animals. Age-related changes in the overall level of response to the afternoon stress were also seen in the corticosteroid and glutathione reductase measures. CONCLUSIONS: The study demonstrated that corticosteroids play an essential role in the regulation of antioxidant enzyme defense in stress conditions and that the reliability of their regulation decreases with age.