Changes in Trace Elements and Enzyme Activities in Tissues of Zinc-Deficient Pigs

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Abstract
Effects of deficiency of zinc were studied in young pigs. Growth retardation was evident by the end of the 1st week and moderately severe parakeratosis was observed by the end of the 2nd week. The weights of most organs decreased in proportion to the body weight. Thymus showed greater decrease, whereas adrenals, pituitary, and kidneys were relatively increased in weight in zinc-deficient pigs. Serum zinc and serum alkaline phosphatase activity were decreased significantly in the zinc-deficient pigs. Zinc content of the bone, pancreas, and liver and activities of various zinc-dependent enzymes, in bone, pancreas, testis, skin, esophagus, and pituitary, were decreased in the zinc-deficient pigs as compared to the restrictively fed controls. Succinic dehydrogenase, an iron-dependent enzyme, showed no differences in its activities between the two groups. Iron content of pancreas, copper in bone and liver, calcium in intestine, and manganese in liver and pancreas were increased in the zinc-deficient group, suggesting physiological competition between zinc and other elements for similar binding sites in the tissues. Our results suggest that in the young pig certain tissues are more susceptible to effects of zinc deficiency than others. Bones and pancreas appear to be very sensitive to zinc lack and it is conceivable that growth retardation is a result of its adverse metabolic effects on these two organs. It is suggested that the content of zinc in various tissues controls the physiological processes through the formation or regulation, or both, of activities of zinc-dependent enzymes.