THE SPECIATION OF LEAD IN ERYTHROCYTES IN RELATION TO LEAD TOXICITY -CASE-STUDIES OF 2 LEAD-EXPOSED WORKERS

Lead toxicity is known to be subject to individual susceptibility. Thi s study compares two lead-exposed subjects, one (A; blood Pb 1800 mug/ L) who remained totally asymptomatic, the other (B; blood Pb 1610 mug/ L) who showed symptoms of toxicity. We have assessed the speciation of lead in the intra-erythrocyte proteins in these patients and have exa mined its significance in relation to clinical toxicity. Chromatograph ic separations of erythrocyte haemolysates from these patients showed a metallothionein-like lead containing protein. It was demonstrated th at in patient A, most (almost-equal-to 70%) of the erythrocyte lead wa s associated with this protein, whilst in patient B the protein only c ontained about 20% of the total lead, with significant amounts bound t o high molecular weight proteins, including Hb. Further purification o f this protein from each patient showed it to contain a number of cons tituents, one in particular being the major lead-binding species. This component was more abundant in patient A and, relative to patient B, contained a higher proportion of lead. These results suggest that this protein may act to sequester lead into a non-bioavailable form, hence protecting the body from lead toxicity as with patient A. (C) 1993 In tox Press, Inc.