Circaannual changes in antioxidants and oxidative stress in the heart and liver in rats

Reactive oxygen species are formed in physiological and pathological condit ions in mammalian tissues. Because of their high reactivity, they may inter act with biomolecules, inducing oxidative injury. Increases in lipid peroxi dation can result in oxidative damage to cellular membranes. Protection aga inst oxidative damage is provided by enzymatic and non-enzymatic antioxidan t defenses. Antioxidant enzyme activities and lipid peroxidation, as an ind ex of oxidative stress injury, were evaluated in different seasons over one year in the heart and liver of rats, maintained on a 12 h light and dark c ycle. Glutathione peroxidase and catalase activities, in both tissues, were maximal in the summer season. Lipid peroxidation in the heart was maximal in the spring as compared to the other seasons and it did not vary in the l iver during the year. These findings suggest that any study of antioxidants or oxidative stress must take into account such seasonal variations for a more precise analysis of changes due to any pathological condition. (C) 200 0 Elsevier Science Inc. All rights reserved.