Age-related changes in activities of the superoxide dismutase enzymes in tissues of the sheep and the effect of dietary copper and manganese on these changes.

Activities of the copper-zinc- and manganese-containing superoxide dismutase enzymes (CuSOD and MnSOD) were studied in tissues of the sheep to determine the dependence of these activities on sheep age, and their relationship to tissue and dietary mineral concentrations. Tissue samples were obtained from day-old through 16-week-old lambs from flocks grazing pastures normal or high in copper and manganese, and from adult sheep. In liver, lung, heart, kidney and skeletal muscle, activities of CuSOD and MnSOD in day-old and week-old lambs were only half those measured in 16-week-old and adult sheep. Activities in 4-week-old lambs were intermediate between these two groups except for heart tissue, in which activities were not increased until lambs were 16 weeks old. For all age groups, heart and skeletal muscle had low activities of CuSOD. Minimal age-related changes were observed for CuSOD activities in erythrocyte and brain tissues. The low enzyme activities evident in most tissues of day-old lambs, occurred in the presence of apparently adequate tissue copper and manganese concentrations. Concentrations of these minerals in lamb tissues were equal to or greater than those observed in older sheep and although these concentrations increased considerably with increased pasture mineral concentrations, enzyme activities were unchanged. Age-related increases in tissue CuSOD and MnSOD activities, occurring as normal developmental processes, may be important factors in diseases attributed to uncontrolled tissue peroxidation in sheep.