Influence of tansy ragwort ( Senecio jacobaea), dietary copper, and feed restriction on the subcellular distribution of minerals in rat liver

Abstract

Young male rats were pair-fed diets containing 0 or 5% tansy ragwort (TR), with each diet containing 0 or 50 μg/g copper. Other animals given TR-free diets were also maintained as ad libitum controls. After 5 weeks of feeding these diets, the rats were killed for the determination of the trace metal contents of liver fractions. TR with no dietary copper supplement increased the calcium content of all hepatic fractions except nuclei and debris, but had no effect on the subcellular concentrations of copper, zinc, or iron. When 50 μg/g copper was included in the TR diet, the subcellular distribution of copper, iron, and calcium was altered. This alteration was shown by an increase (as compared to pair-fed controls given copper-supplemented diet with no TR) in the copper content of all fractions except cytosol, the iron content of all fractions, and the calcium content of mitochondria, microsomes, lysosomes, and cytosol. Feed restriction (pair-fed versus ad libitum controls) using diets with no additional copper produced an increase in the copper and calcium contents of mitochondria; the copper, zinc, and calcium contents of cytosol; and the calcium content of lysosomes. Addition of 50 μg/g copper to the diets abolished these effects of feed restriction. These findings suggest that the subcellular distribution of copper, zinc, iron, and calcium in rat liver is subject to perturbation by pyrrolizidine alkaloid-containing diet, dietary copper, and feed restriction.