Enzyme Activities in Tissues of Zinc-deficient Rats

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Abstract
Activities of 1) alcohol and glutamic dehydrogenase in liver and kidney, 2) alkaline phosphatase in intestinal mucosa, kidney, and plasma, 3) catalase in liver, kidney, and blood, 4) xanthine oxidase in liver and kidney, and 5) aspartic and alanine aminotransferases in liver were measured in rats fed diets low in zinc or protein, or both, and in their pair-fed controls for 45 to 180 days. Deficient diets contained either 1 to 2 or 2 to 4 ppm of zinc; control diets, 20 or 30 ppm. Alkaline phosphatase activity decreased (together with zinc concentration) in the intestinal mucosa of rats fed 2 to 4 ppm but not in plasma or kidney. Addition of 0.5 mmoles of zinc increased activity to the same extent in mucosal homogenates of zinc-deficient and control rats. Alcohol dehydrogenase activity in liver decreased marginally in rats receiving 2 to 4 ppm of zinc and substantially in those receiving 1 to 2 ppm. A correlation existed between alcohol dehydrogenase activities and zinc concentrations in livers of the latter. Lowered glutamic dehydrogenase activities of marginal significance occurred in kidney when 2 to 4 ppm diets were fed with 14.8% protein. No changes occurred in activities of the other enzymes. Elevated concentrations of uric acid in plasma occurred infrequently. Only zinc-dependent enzymes suffered impairment of activity in zinc deficiency. The lowered activity is attributed to decreased enzyme concentrations. Lack of sufficient zinc to maintain the structural integrity of these enzymes is suggested as a cause.