HORMONAL MODULATION OF ANTIOXIDANT ENZYME-ACTIVITIES IN YOUNG AND OLDRATS

The correlation between serum levels of pituitary and thyroid hormones and the activity of two antioxidant enzymes (AOE), catalase (CAT) and superoxide dismutase (SOD), in different immune and nonimmune organs of young and old rats was investigated. Serum levels of growth hormone (GH), prolactin (Prl), thyroid-stimulating hormone (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroxine (T-4), an d triiodothyronine (T-3) as well as the activity of AOE in liver (CAT and SOD), spleen (CAT and SOD), thymus (SOD) and mammary tissue (SOD) were determined in 7- and 29-month-old Sprague-Dawley female rats. A m arked hyperprolactinemia and lower levels of TSH, LH, FSH and GH were observed in the old rats when compared to the young ones (p < 0.05). O ld animals showed a higher SOD activity in liver and thymus but a lowe r activity in spleen than their young counterparts (p < 0.05). In addi tion, CAT activity in spleen was lower in old than in young rats (p < 0.05). The Spearman's test revealed a positive correlation between: 1) serum levels of TSH and the activity of SOD in liver and 2) serum lev els of Prl and GH and the activity of SOD in mammary tissue of young a nd old animals (p < 0.05). Likewise, CAT in liver showed a highly sign ificant correlation with serum TSH (but not T-4 and T-3) levels in you ng (p < 0.01) but not in old rats. Our results confirm that aging is a ssociated with alterations in the endocrine balance and the activity o f AOE in lymphoid as well as in nonimmune organs. In addition, our fin dings suggest that Prl and GH may be physiological modulators of mamma ry SOD activity, and that TSH can possibly influence the activity of b oth CAT and SOD in liver via a thyroid-independent pathway. Furthermor e, our data show that, when significant, the correlation between hormo ne levels and AOE activity deteriorates with age.