The effect of calcium on lead absorption in rats

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Abstract
Effects of Ca2+ on Pb absorption as PbCl2 and 203PbCl2 were studied in rats. Doubling of dietary Ca with Ca3(PO4)2 significantly decreased Pb absorption as assessed by 203Pb retention, tissue Pb concentration, urinary excretion of .delta.-aminolevulinate and increased activities of .delta.-aminolevulinate dehydratase and ferrochelatase. Similar effects on Pb absorption were shown by the Ca2+ salts, Cl-, CO32-, PO43-, SO42-, gluconate and glycerophosphate. CaCl2 and calcium glycerophosphate were most effective in decreasing Pb absorption when administered immediately before Pb dosage. A negative exponential relationship was found between CaCl2 concentration and 203Pb absorption at 120 h. Results suggest that, above 4 mmol of administered Ca, residual Pb absorption is unaffected by increasing gastrointestinal Ca concentrations. Increased systemic Ca had no effect on Pb retention. Ca in the concentrations found in domestic hard water supplies significantly decreased absorption of a solution of 203Pb dissolved in it compared with absorption of 203Pb dissolved in soft or distilled water. Milk and skimmed milk had no effect on 203Pb absorption in rats.