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Our study concerns the effects of exposure to lead chloride on the morphology, K+ efflux, SO4 − influx and GSH levels of the human erythrocyte. Blood was collected in heparinized tubes and washed three times. The cells were suspended at 3% hematocrit and incubated for 1 h at 25°C in a medium containing increasing concentrations of lead chloride (0, 0.3, 0.5 and 1 μM). After incubation, the suspensions were centrifuged and the erythrocyte pellets were divided into three aliquots for testing. The results show: an increase in the permeability of erythrocytes treated with lead chloride with consequent damage and cellular death, especially in the presence of high concentrations; an increase in potassium ion efflux; alterations in the morphology and membrane structure of the red blood cells; and a decrease in sulphate uptake, due either to the oxidative effect of this compound on the band 3 protein, which loses its biological valence as a carrier of sulphate ions, or to a decrease in the ATP erythrocyte concentration. In conclusion, the exposure of erythrocytes to Pb2+ ions leads to a reduction in the average lifetime of the erythrocytes and the subsequent development of anemia. These data are discussed in terms of the possible effect of lead on the reduction-oxidation systems of the cell. Oxidant agents, such as lead, are known to cross-link integral membrane proteins, leading to K/Cl-cotransport. The increased K+ efflux affects the altered redox state.
The effect of organophosphorus insecticides malathion and parathion as well as their main metabolites malaoxon and paraoxon on chloride (36Cl-) and sulfate (35SO42-) equilibrium exchange in pig erythrocytes was investigated using an isotope labelling technique. Efflux of both radioactive isotopes vs. time followed a single exponential. Parathion and paraoxon inhibited the chloride equilibrium exchange in intact ceils in a dose- and time-dependent manner. There was no difference between effects evoked by these two compounds. Neither malathion nor malaoxon affected the chloride transport. Parathion and paraoxon inhibited sulfate efflux from resealed ghosts. The effect was also dose- and time-dependent. Again, there was no difference between action of the agents. No effect of malathion and malaoxon on sulfate efflux was observed. Dixon analysis revealed noncompetitive character of the inhibition of the exchange of both anions with the apparent Ki, values 68 and 73 µM for parathion and paraoxon, respectively in the case of chloride transport; for sulfate exchange these values were 341 and 340 µM, respectively. It was suggested that structural similarity between parent agents and their metabolites is responsible for the identity of their effects. Parathion and paraoxon could inhibit the anion exchange indirectly by changing the fluidity of the erythrocyte membrane or directly by binding to the Band 3 protein and evoking conformational changes leading to the inhibition of the anion transport. The insecticides, due to their ability to phosphorylate, could also disturb some regulation processes in the Band 3 protein.
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