Cytochrome Oxidase in Mice and Rats Maintained with a Meat Diet

Abstract

Young mice and rats were fed for 6 weeks either a meat diet offered unsupplemented or supplemented with copper, calcium and zinc or certain combinations of these, or a nutritionally adequate semipurified diet. Copper concentration of liver and cytochrome oxidase activity of liver and kidney were decreased in animals fed meat in comparison with those of controls. No close correlation was found between the activities of cytochrome oxidase of liver and kidney. Supplementation of meat with calcium or copper increased activity of cytochrome oxidase of liver, whereas zinc decreased it. Calcium and copper raised the level of liver copper and lowered that of liver zinc. In mice, but not in rats, reduction of copper and cytochrome oxidase in liver were accompanied by anemia. The addition of copper to liver homogenate from rats fed meat had no significant effect on the low cytochrome oxidase activity; cytochrome oxidase was not affected by the addition of zinc to homogenates of liver from rats fed meat plus copper. It is concluded that the decreased activity of liver cytochrome oxidase of mice and rats subsisting on meat results from an excess of zinc which is insufficiently counteracted by copper and accentuated by a concomitant lack of calcium. The adverse effect of excess of zinc on erythrogenesis is not mediated through its action on cytochrome oxidase.