Effect of Supplementary Zinc on the Intracellular Distribution of Hepatic Copper in Rats

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Abstract
Thirty weanling rats were divided into five groups and were fed a ration containing 6 ppm copper or this ration supplemented with 1,000, 2,000, 4,000, or 8,000 ppm zinc as zinc carbonate. After 10 weeks on these diets, the rats were killed for determination of zinc and copper levels in the whole livers and in the intracellular fractions. There was a significant correlation between liver zinc levels and the dietary levels. The accumulation of zinc in the liver resulted in a two-phase depression of hepatic copper. The addition of up to 2,000 ppm dietary zinc resulted in a linear decrease in liver copper levels, but the addition of zinc above 2,000 ppm resulted in a further decrease at a slower rate. Increasing dietary zinc levels had no influence on the hepatic copper content of the nuclei and debris, and mitochondria, but this element significantly depressed the copper levels in the microsomes and the soluble fraction. Likewise, elevated dietary zinc did not affect the zinc levels in the nuclei and debris, and mitochondria, but the levels of this element were significantly increased in the microsomes and the soluble fraction. The percentage dialyzable copper in the soluble fraction decreased with each level of increase in dietary zinc.