Dietary regulation of copper absorption and storage in rats: effects of sodium, zinc and histidine-zinc.

Zinc (Zn) and L-histidine (His) are known competitors of intestinal copper (Cu) uptake. Sodium (Na) appears to be an enhancer of the luminal phase of Cu absorption. We investigated whether dietary treatment with these modifiers would alter Cu absorption and tissue stores of Zn and Cu in rats. Juvenile male rats were fed semipurified diets with adequate amounts of Cu, Zn and Na (Ctl), or with the addition of either excess Na (Hi Na), Zn (Hi Zn), or Zn plus His (Hi Zn+His) for 3 weeks. The jejunum was perfused in situ with 0.1 mM Cu, 1 mM His to determine Cu and water absorption rates. The lowest Cu absorption rate was observed in the Hi Zn+His group, and both the Hi Zn and Hi Zn+His had greater Cu accumulation in the small intestine than did Ctl or Hi Na rats. Hi Na had no effect on Cu transport. There was excess Cu accumulation in the kidneys of Hi Zn+His rats, and hepatic and kidney metallothioneins were also elevated. These results indicate that while a high Na intake does not affect Cu absorption, excess dietary Zn and His have greater effect than does Zn only in the limitation of Cu uptake.