Abstract
Erythrocytes from young and old rats were separated into four age fractions by density-gradient centrifugation. The specific activities per cell were determined for glucose-6-phosphate dehydrogenase (EC 1.1.1.49), glutathione peroxidase (EC 1.11.1.9), glutathione reductase (EC 1.6.4.2) and catalase (EC 1.11.1.6). Decreased specific activities were observed with increasing cell age for all four enzymes in both young and old animals. In addition, significant differences in the activities of these enzymes were observed between cells of the same age fraction from young and old donors. Susceptibility of fractionated erythrocytes to oxidative attack in vitro generated by incubation with xanthine/xanthine oxidase increased with both cell and animal age. The amount of membrane-lipid peroxidation also increased with cell and animal aging, as measured by both thiobarbituric acid and fluorescent chromolipid assays. Increases of 2-3-fold in the contents of lipid peroxides were observed between the youngest and oldest age fractions of young rats. Lipid peroxide contents in young cells of old animals were equal to those in old erythrocytes from young rats and increased by 30% with cell aging in the old donors. These results suggest that the extent of enzymic protection against oxidative and peroxidative damage decreases with erythrocyte aging. More importantly, enzymic protection in cells of old rats is considerably decreased already in the early stages of their lifespan.