Effect of triiodothyronine on reactive oxygen species generation by leukocytes, indices of oxidative damage, and antioxidant reserve

We have examined the effect of short-term triiodothyronine (T-3) administra tion on reactive oxygen species (ROS) generation by leukocytes in 9 euthyro id subjects. At a dose of 60 mu g/d orally for 7 days, T-3 induced a signif icant increase in ROS generation by mononuclear cells (MNCs) from 183 +/- 1 02 mV at baseline to 313 +/- 111 mV on the seventh day (P < .02), and by po lymorphonuclear leukocytes (PMNLs) from 195 +/- 94 mV at baseline to 302 +/ - 104 mV on the seventh day (P < .02). There was also a significant increas e in meta-tyrosine (P < .001) and ortho-tyrosine (P < .001), known indices of oxidative damage to proteins and amino acids. However, there was no incr ease in plasma thiobarbituric acid-reactive substances (TBARS), an index of oxidative damage to lipids, and in the level of carbonylated proteins, a l ess sensitive index to assess protein oxidation, There was no decrease in t he level of antioxidants such as alpha-tocopherol, vitamin A, beta-carotene , lycopene, and lutein/zeaxanthin. The stimulatory effect on ROS generation may reflect a generalized increase in metabolic activity or may be a speci fic effect on NADPH oxidase in leukocyte membranes. The absence of a signif icant change in TEARS, carbonylated proteins, alpha-tocopherol, vitamin A, beta-carotene, lycopene, and lutein/zeaxanthin may reflect the short durati on of the increased ROS load. Copyright (C) 2000 by W.B. Saunders Company.