Isotope dilution measurement of copper absorption and excretion in rats fed different carbohydrates

An isotope dilution method using 67Cu was developed to measure true absorption (A) and endogenous excretion (EE) of Cu in rats. Specific activity (SA) of injected 67Cu was least variable in 7 tissues on days 6-8 after injection. SA of feces compared to tissues was used to calculate EE and A. This method was used to study Cu metabolism in rats fed 5 ppm or 0.4 ppm Cu and diets containing fructose (FR), glucose (GL), sucrose (SU), or cornstarch (CS). In rats fed 5 ppm Cu, the A, EE, and balance (B) were greatest for CS animals. There were no differences in A, B, or EE between FR and SU rats (p > .05). Rats fed GL had B and A lower than other groups (p < .05) but EE was different only from CS rats. Liver and kidney Cu and ceruloplasmin levels were highest in CS rats; other groups did not differ significantly. For rats fed 0.4 ppm Cu, the A, B, and EE did not differ among groups fed different carbohydrates (p > .05). Liver Cu did not differ among groups fed 0.4 ppm Cu. Kidney Cu was higher ( p < .001) in CS rats than GL rats; other groups did not differ. B was significantly lower in rats on the 0.4 ppm Cu diet than on 5 ppm Cu for CS, FR, SU (p < .05). Rats fed the GL-low Cu diet had significantly higher A (p < .01) and unchanged B (p > .05) compared to rats fed GL and 5 ppm Cu. EE was significantly lower in all groups on 0.4 ppm Cu than 5 ppm Cu. EE was 1 μg Cu/d on the 0.4 ppm Cu diet