Regulation of superoxide dismutase activity by dietary manganese

The activity of superoxide dismutase in rats, mice and chickens fed purified diets containing various levels of manganese has been studied. In liver of manganese-deficient mice, the activity of CN-insensitive manganese superoxide dismutase was only 17% of that found in control mice. In the brain, superoxide dismutase activity was reduced by 50% of the manganese-deficient mice. In manganese-deficient rats, activity of this enzyme was not affected. Chickens fed a manganese-deficient diet from hatching had significantly lower levels of CN^--insensitive mangano-superoxide dismutase activity in liver than did controls. However, activity of the cupro-zinc superoxide dismutase in liver was higher in manganese-deficient chickens than in controls. The activity of both forms of superoxide dismutase reached normal levels when a manganese-supplemented (1,000 ppm) diet was fed to deficient chickens, but the activity of the manganese enzyme was not affected by feeding the supplemented diet to manganese-sufficient chickens. The liver concentration of manganese was significantly decreased by dietary deficiency, but no changes occurred in the concentration of copper and zinc. It is concluded that dietary manganese can act to regulate the activity of the CN^--insensitive superoxide dismutase and that this enzyme form and the CN^--sensitive one, although compartmentalized, are not independently regulated. Compensatory changes in their activities occur in fact, probably induced by the intracellular concentration of O₂ ^-.