The speciation of lead in erythrocytes in relation to lead toxicity: case studies of two lead-exposed workers.
Lead toxicity is known to be subject to individual susceptibility. This study compares two lead-exposed subjects, one (A; blood Pb 1800 micrograms/L) who remained totally asymptomatic, the other (B; blood Pb 1610 micrograms/L) who showed symptoms of toxicity. We have assessed the speciation of lead in the intra-erythrocyte proteins in these patients and have examined its significance in relation to clinical toxicity. Chromatographic separations of erythrocyte haemolysates from these patients showed a metallothionein-like lead containing protein. It was demonstrated that in patient A, most (approximately 70%) of the erythrocyte lead was associated with this protein, whilst in patient B the protein only contained about 20% of the total lead, with significant amounts bound to high molecular weight proteins, including Hb. Further purification of this protein from each patient showed it to contain a number of constituents, 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.
Church
H J
HJ
Department of Chemistry, University of Manchester, England.
Day
J P
JP
Braithwaite
R A
RA
Brown
S S
SS
D000328:Adult; D002352:Carrier Proteins / Q000097:blood; D004912:Erythrocytes / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D006801:Humans; D007855:Lead Poisoning / Q000097:blood*; D008297:Male; D008668:Metallothionein / Q000097:blood; D008875:Middle Aged; D016273:Occupational Exposure; D011485:Protein Binding
D002352:Carrier Proteins; D008668:Metallothionein