Plasma and blood lead in humans: capacity-limited binding to delta-aminolevulinic acid dehydratase and other lead-binding components.
In 42 lead-exposed workers (22 male and 20 female), we found a close nonlinear relation between blood and plasma lead concentrations, determined by inductively coupled plasma mass spectrometry (ICP-MS). The concentration medians and ranges were lead in whole blood, 270 (97 to 950) micrograms/L and lead in plasma, 1.1 (0.2 to 13) micrograms/L. Proteins from lysed erythrocytes were studied by gel chromatography with ICP-MS detection. We then found capacity-limited binding for lead to delta-aminolevulinic acid dehydratase (ALAD), as well as to two other components (with apparent molecular masses of 45 and < 10 kDa, respectively). The strongest affinity for lead was indicated for ALAD (35-81% of the lead in blood) and could be described by a capacity of 850 micrograms/L and a dissociation constant of 1.5 micrograms/L. The 45-kDa protein carried 12-26% of the blood lead, and the < 10-kDa component less than 1%. A model based on these three components, plus a fourth one for unrecovered lead (2-45%), is proposed. No binding of lead to hemoglobin was found. There was an association between zinc and lead in whole blood; however, zinc did not significantly affect the lead distribution in erythrocytes.
Department of Occupational and Environmental Medicine, Lund University, Sweden.
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Bergdahl
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Sheveleva
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Schütz
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VG
Artamonova
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Skerfving
D002850:Chromatography, Gel; D004347:Drug Interactions; D005260:Female; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D007854:Lead / Q000097:blood*; D008297:Male; D013058:Mass Spectrometry; D008954:Models, Biological; D016273:Occupational Exposure / Q000009:adverse effects*; D000623:Porphobilinogen Synthase / Q000378:metabolism*; D011485:Protein Binding; D015032:Zinc / Q000378:metabolism*
D006454:Hemoglobins; D007854:Lead; D000623:Porphobilinogen Synthase; D015032:Zinc