Lead was administered to Long-Evans rats by daily oral gavage for 30 days at doses of 200, 400, or 600 mg lead/kg/day. The rats were then administered one of the radiolabeled insecticides and the metabolic products examined. The lead-treated rats had blood lead concentrations of ca. 200 μg/dl in the 200 mg/kg/day group and ca. 475 in the 400 mg/kg/day group. Concentrations of lead in the femur were 500 μg/g or higher. Despite this high body burden of lead (accompanied by a 30% weight deficit at 600 mg/kg/day), no difference in the rate of elimination of radiolabeled material was observed. Furthermore, the lead treatments did not change the relative proportions of the detected metabolites. Thus, despite the known effects of lead on heme synthesis, these treatments had no detectable effect in vivo on the metabolism of propoxur or malathion.
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