Aging and lung antioxidant enzymes, glutathione, and lipid peroxidation in the rat.

The five major antioxidants enzymes, cytochrome oxidase (COX), GSH, and GSSG, and endogenous and in vitro stimulated lipid peroxidation (TBA-RS) were assayed in the lung of old (28 months) and young (9 months) adult rats due to the almost total absence of data of this kind in this tissue, which is normally exposed to relatively high pO2 throughout life. Catalase, selenium (Se)-dependent GSH peroxidase (GPx), GSH reductase, GSH, GSSG, GSSG/GSH, and in vivo and in vitro TBA-RS showed similar values in old and young animals. The decrease observed for non Se-dependent GPx disappeared when the values were expressed in relation to COX activity. Only superoxide dismutase showed a clear decrease when referred both to protein and COX activity. These results suggest that lung aging is not accelerated in old age due to a decrease in the antioxidant capacity of the tissue. Nevertheless, they are compatible with a continuous damage of the lung tissue by free radicals throughout the life span.