Copper status of adult male rats is not affected by feeding an AIN-93G-based diet containing high concentrations of zinc

Abstract

Although previous studies have shown that copper status of rats is compromised when they consume a diet with high zinc, studies using the new AIN-93G rodent diet did not show this effect. Because the new diet formulation contains components such as L-cystine and an ultratrace element (UTE) mix that might affect copper metabolism, a study was done to determine if these components interfered with the effect of zinc. A 2 × 2 × 2 × 2 factorial study was designed with two dietary concentrations of copper, 3 and 6 mg/kg of diet; with L-cystine or DL-methionine; with or without the UTE mix; and with 2 concentrations of zinc, 35 and 350 mg/kg of diet. After 5 weeks, assessments of copper status were made. Results showed that serum ceruloplasmin amine oxidase activity, a very sensitive copper status indicator, was not affected by feeding high zinc in the diet. Other status indicators such as serum copper or liver copper concentrations also were not affected by high-zinc feeding. It was concluded that the lack of an effect of high zinc on copper status when using the AIN-93G diet was not the result of using L-cystine or UTE in the diet. Dietary UTE stimulated growth in rats fed the marginal-copper diet but not in rats fed the normal-copper diet. Rats fed diets containing DL-methionine had significantly higher concentrations of liver and intestinal copper than those fed diets with L-cystine.