IMPLICATIONS OF LEAD BINDING-PROTEINS FOR RISK ASSESSMENT OF LEAD-EXPOSURE

Lead-binding proteins have previously been isolated from rat and human target tissues. These molecules have shown to possess molecular masse s in the general range of 10,000-30,000 daltons. The proteins are acid ic in nature and rich in aspartic and glutamic amino acid residues. Th e molecules in rodents appear to play several important roles in media ting the low dose toxicity of lead in the kidney and brain. Preliminar y studies presented in this report indicate that monkeys also possess similar proteins in the kidney and brain, thus providing a biochemical ''bridge'' in a non-human primate between rodent models and humans. F urther, the excretion of these molecules into the urine of rodents inc reases with lead exposure, suggesting they may also prove useful as bi omarkers of lead exposure in humans and monkeys once the dose-range an d mechanism(s) of this phenomenon are further defined. Such studies sh ould provide valuable risk assessment information for determining why individuals vary in their susceptibility to lead toxicity.