Lead toxicity and heme biosynthesis

Lead intoxication results in a disturbance of heme biosynthesis, its degree depending on the severity and duration of exposure to lead. A mild secondary, sideroblastic anemia is common; basophilic stippling may occur, especially in severe lead poisoning. Increased excretion in the urine of delta-aminolevulinic acid and coproporphyrin III may occur; porphobilinogen excretion is not usually increased. Delta-aminolevulinate dehydratase, coproporphyrin oxidase, and ferrochelatase activities are reduced; delta-aminolevulinate synthetase activity is increased. Erythrocyte protoporphyrin (FEP and ZPP) is increased. Recent knowledge of the heme biosynthetic enzymes is reviewed and the significance of FEP and ZPP discussed. A brief history is given of the relationship of lead toxicity to the porphyrins.