THE PH-DEPENDENCE OF SILICON-IRON INTERACTION IN RATS

A 2 x 2 x 3 factorial experiment was conducted to study the pH depende nce of a silicon-iron interaction in vivo. The dietary treatments used in the factorial design were the following (mg/kg of diet): silicon, 0 and 500; iron, 35 and 187; acid-base, ammonium chloride as 0.5% of t otal diet (acidic), sodium bicarbonate as 1.0% of total diet (basic), or no supplementation of acid or base (control). The supplementation o f 500 mg silicon/kg of diet increased plasma-iron concentration in rat s fed the acidic or control diets, but not in rats fed the basic diet. A high dietary-iron level suppressed copper absorption and utilizatio n and subsequently imposed a negative effect on its own utilization. A n increase in the plasma total-cholesterol concentration caused by hi, oh dietary-iron level was likely a consequence of the antagonistic eff ect of iron on copper absorption and utilization. The use of cupric su lfate pentahydrate as the dietary-copper source in this study resulted in plasma copper concentrations that were approximately twice those o btained in a related study using cupric carbonate. Also, a 42% coeffic ient of variation (C.V.) for plasma-copper concentrations of rats fed cupric sulfate in this study was greatly reduced from the C.V. = 108% previously associated with the dietary cupric carbonate.