The effects of dietary calcium on lead absorption, distribution, and elimination kinetics in rats.

A pharmacokinetic analysis of lead absorption, distribution, and elimination was conducted in rats maintained on calcium-deficient, control, and calcium-supplemented diets. Dietary calcium affected lead disposition in a number of ways. Systemic lead clearance after a 10-mg/kg intracardiac lead dose was approximately 25% lower than control in rats administered dietary calcium supplements. Intestinal absorption of 10 mg/kg po lead doses was not affected by the calcium supplements. In rats maintained on a calcium-deficient diet, systemic lead clearance was estimated to be 40% less than control. The apparent volume of lead distribution was increased. The apparent systemic availability of 1-, 10-, and 100-mg/kg oral lead doses was three- to fourfold greater than control in calcium-deficient rats. The percentage absorption was dose-dependent in control and calcium-deficient rats. The observed changes in lead absorption and systemic clearance associated with the calcium-deficient diet represent synergistic effects that could elevate blood lead accumulation and thus potentially influence susceptibility to lead toxicity.