Distribution of lead-203 in human peripheral blood in vitro.

Abstract

In-vitro experiments using 203Pb were performed to identify the lead binding components in human peripheral blood. The distribution of lead in plasma, in the red cell membrane, and within the red cell was also investigated. Studies of the distribution of 203Pb in whole blood showed that at a lead concentration of 2 45 ,umol/l (50 ug/100 ml) about 94 % of lead had been incorporated by the erythrocytes and 6 % remained in the plasma. responsible for the lead uptake; one is protein and the other a non-protein, probably a phenolic compound. This hypothesis has been discounted by Clarkson and Kench,4 who suggested that lead exists in the blood as a peptised lead phosphate-sol, the groups of which are probably aggregated on the surface of the cell to form a larger particulate. On the other hand, recent studies by Barltrop and Smith7 8 using tracer 203Pb do not confirm that lead has an affinity to the red blood cell membrane. These authors separated the 203Pb-containing fraction of RBC by sephadex gel filtration and ultracentrifugation. Lead was found attached to the intracellular constituents rather than the stromal membrane, and to a molecule similar in size to the haemoglobin polypeptide. White,9 however, and Selhi and White'0 believe that the attachment takes place in the erythrocyte membrane, which results in alteration of membrane protein conformation.The identification of specific lead binding sites in the blood is hindered by experimental difficulties such as the necessity to detect and to measure trace amounts of lead in microsamples of subcellular 78

Biomarkers of Lead Exposure.

“…They suggested that the membranebound lead might affect the activity of Na, K-ATPase. Several workers [23][24][25] have indicated that most of the labeled lead incorporated into erythrocytes in vitro is found in hemoglobin fractions. By contrast, Sakai et al 20,66) reported that half the lead in erythrocyte hemolysate from a lead-exposed worker was found in protein fractions with a high molecular weight, including ALAD, which had highest affinity for lead among erythrocyte components in vivo and in vitro.…”

Lead Binding to δ‐Aminolevulinic Acid Dehydratase (ALAD) in Human Erythrocytes

“…The accumulation of lead in erythrocytes has been ascribed to its affinity for haemoglobin. since various studies of lead-binding proteins indicated that lead bound almost exclusively to haemoglobin (Ong & Lee 1980;Barltrop & Smith 1971;Raghavan & Gonick 1977;Lolin & O'Gornian 1988;Church et a/. 1993).…”

Characterizing Golden Eagle Risk to Lead and Anticoagulant Rodenticide Exposure: A Review

“…Approximately 40-75% of lead in the plasma is bound to plasma proteins, of which albumin appears to be the dominant ligand (Al-Modhefer et al 1991;Ong and Lee 1980a). Lead may also bind to γ-globulins (Ong and Lee 1980a). Lead in serum that is not bound to protein exists largely as complexes with low molecular weight sulfhydryl compounds (e.g., cysteine, homocysteine) and other ligands (Al-Modhefer et al 1991).…”

“…Most of the lead found in red blood cells is bound to proteins within the cell rather than the erythrocyte membrane. Approximately 40-75% of lead in the plasma is bound to plasma proteins, of which albumin appears to be the dominant ligand (Al-Modhefer et al 1991;Ong and Lee 1980a). Lead may also bind to γ-globulins (Ong and Lee 1980a).…”

“…the formation of complexes with amino acids and nonprotein thiols, and binding to various proteins (DeSilva 1981;Everson and Patterson 1980;Goering and Fowler 1987;Goering et al 1986;Ong and Lee 1980a, 1980b, 1980cRaghavan and Gonick 1977).…”