Influence of chronic zinc supplementation on biochemical, variables and circadian rhythms in Wistar rats

The effects of chronic zinc supplementation to Wistar rats at two doses (el emental) 50mg/g of diet (group-I) and 400mg/g of diet (group-II) on (i) lip id peroxidation status, superoxide dismutase activity, iron, and ceruloplas min levels and (ii) circadian oscillations of glucose, total protein, alkal inephosphatase activity and thiobarbituric acid reactive substances were in vestigated. Iron in tissues (liver & kidney), ceruloplasmin, thiobarbituric acid reactive substances in plasma and tissues were found to be decreased in zinc supplemented groups. Superoxide dismutase activity in liver of grou p-I animals was increased but slightly decreased in group-II animals. Zinc might competitively inhibit the iron uptake by ferritin thereby reducing th eir levels. The increased activity of superoxide dismutase (in group I) mig ht be due to induction/stabilisation of the enzyme by zinc. Induction of me tallothionein and modulation of iron and copper levels during zinc suppleme ntation might lead to low levels of lipid peroxidation. The peak time of ci rcadian oscillation of total protein was delayed by three hours (during zin c supplementation). This might be due to altered positive or negative balan ce between synthesis and degradation of protein during zinc supplementation . (C) 2000 Elsevier Science Inc.