Lead and Vitamin Effects on Heme Synthesis

Abstract

When a purified diet was supplemented with 300 ppm lead as the acetate and was fed to weanling rats, significant decreases in feed intake, weight gain, and blood heme were observed. In vitro heme synthesis in blood from these lead-treated animals was increased by a single injection of niacin or vitamins C + B₁₂; pyridoxine, thiamine, or riboflavin had no effect. Exposure to diet lead concentrations of 50, 150, and 300 ppm produced a significant and graded increase of urinary δ-aminolevufinic acid (ALA) within 18 hours, followed by a gradual decrease. A tenfold dietary excess of niacin provided no significant protection against toxic reactions from lead in terms of in vivo blood heme levels, in vitro heme synthesis, or urinary ALA.