The effect of some protein solutions on the oxidation of glutathione in oxygenated erythrocytes

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Abstract
When intact washed human erythrocytes are oxygenated, e.g. in saline (0.9% NaCl solution), glutathione is converted into its oxidized form. Some of this is then slowly lost by an unknown route. The rate of the oxidation is greater when the oxygenation is carried out in human-serum-albumin (HSA) or bovine- [gamma]-globulin solutions than when it is carried out in bovine-serum-albumin or saline solutions. In HSA solutions, the maximum stimulant effect is obtained at a protein concentration of 0.6- 0.8 g/100 ml. and this is unaffected by previous oxidation of the albumin thiol group. The rate of oxidation of glutathione is unrelated to the oxyhemoglobin level of the cells during the oxygenation. The rate of oxidation in erythrocytes oxygenated either in saline or in HSA solution is increased treating the cells with carbon monoxide. The rate of oxidation of glutathione in erythrocytes oxygenated in dialysed serum, prepared from human plasma after dialysis for 3-24 hr., is similar to the rate for the same cells oxygenated in saline. If the dialysed serum is preheated at 70[degree] or prepared after dialysis of plasma for e.g. 44 hr., the rate is then similar to that found for the same cells oxygenated in HSA solution. The time of heating at 70[degree] required to change the rate of oxidation in the same cells from that in saline to that in HSA solutions increases as the time of dialysis decreased. The rate of oxidation of glutathione in oxygenated erythrocytes is reduced by lowering the temperature by 14[degree], more so when the oxygenation is carried out in HSA solution than when it is carried out in saline or dialysed serum. The effect of progressively diluting dialysed serum with HSA solution on the rate of oxidation of glutathione in erythrocytes oxygenated in the dialysed serum-albumin mixtures has been studied. The evidence suggests that human serum contains a heat-labile protein and a slowly diffusible substance which together inhibit the stimulant effect of HSA on the oxidation of glutathione in erythrocytes. The mechanism of this inhibition and its possible role in metabolism are discussed.