Some Biochemical and Clinical Aspects of Lead Intoxication

Abstract

The effects of nutrition on lead intoxication have been poorly studied. The neurologic signs of lead exposure have been given little etiologic explanation, and to a considerable extent, the significance of lead in various organ systems has been poorly characterized. The major biochemical effects of lead on the organism can be broadly grouped into three classes. First, lead has a high affinity for sulfhydryl groups. It is this effect which leads to the inhibition of various sulfhydryl-dependent enzymes, most notably δ-aminolevulinate dehydratase and ferrochelatase, two enzymes in the heme synthetic pathway. Second, divalent lead is similar in some respects to divalent calcium and its competitive action against calcium affects, among other systems, mitochondrial respiration and various neurologic functions. Third, lead has effects on desoxyribonucleic acid and ribonucleic acid, the mechanisms of which are not as yet known but these effects may have important biological implications. The heme pathway, the nervous system, the kidney, and the nucleic acid systems are not each affected solely via a single mode of action. It is found that lead toxicity is modulated by many factors. Children and adults absorb lead to different degrees, express toxicities at different levels of lead absorption, and present with different clinical syndromes. Several assays are available to evaluate the extent of lead exposure. These depend on direct determination of lead, or the biological effects of lead.