Abstract
This study was designed to determine the rate of ingress and egress of erythrocyte lead. Heparinised human whole blood was mixed with solutions of lead chloride (50ug/100ml) labelled with Pb-203. Reentry of lead to the cell was blocked with CaNa2 EDTA 10−4 at measured intervals and the partition between cells and plasma determined by counting at the photopeak (0.279 MeV). Uptake from plasma approaches equilibrium after 15m but egress is prolonged with T1/2 of 120m. Distribution is governed by two variables - duration of contact with lead and duration of elution with the chelating agent. Extrapolation to zero time (T0) revealed a discrepancy of 5% between observed and theoretical lead content of the cells. Cooling the system to 4°C increased the observed discrepancy and inhibited release of lead already bound. The data are consistent with the existence of two cellular binding sites differing in their accessibility to chelating agents, in their affinity for lead, and in the temperature dependence of the rate constants of the associated equilibria. A hypothetical 2-compartment model is presented.
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Barltrop, D., Smith, A. Kinetics of Lead transport across the erythrocyte membrane. Pediatr Res 8, 915 (1974). https://doi.org/10.1203/00006450-197411000-00095
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DOI: https://doi.org/10.1203/00006450-197411000-00095