Mercury Vapor Uptake and Oxidoreductases in Erythrocytes
The inhibition by ethanol of the absorption of inhaled Hgo suggested the participation of catalase in this process (Nielsen-Kudsk, 1969). The studies reported there specified the mechanisms by which H2O2-metabolizing enzymes in erythrocytes enhance or reduce the accumulation of Hg after exposure to Hgo.
When red-blood-cell suspensions were exposed to Hgo in a closed system, it was found that the mercury was absorbed by the cells only. Thus, a low hematocrit led to a high cellular Hg uptake, alterations of which could therefore be analyzed easier. The uptake was inducible by slow infusion of small amounts of H2O2 and paralleled the activity of catalase as was shown by selecting red cells from species with largely different H2O2-metabolizing enzyme activities. The instrumental function of the catalase- H2O2 intermediate (compound-I) in Hg uptake was further verified by its sensitivity to ethanol or aminotriazole (AT).
The essentiality of H2O2 as a cofactor strongly suggested a modulation of Hg uptake by glutathione and its peroxidase (GSH/GSH-Px). GSH-dependent H2O2 removal was inactivated by conjugation of GSH to chlorodinitrobenzole or by t-butylhydroperoxide (t-BOOH) as substrate for GSH-Px. Both treatments significantly enhanced that uptake which could be stimulated by exogenous H2O2. Yet the presence of t-BOOH strongly augmented the Hg uptake even without added H2O2. As this augmentation was sensitive to AT, it probably resulted from compound-I formed by endogenous H2O2 production.
The experiments made evident that elemental Hg is oxidized by a peroxidatic reaction with catalase, a process which is enhanced by the inactivation of the GSH/GSH-Px system.
KeywordsHuman Erythrocyte Mercury Vapor Atomic Mercury Mercury Uptake Iron Cycle
Unable to display preview. Download preview PDF.
- Clarkson, T. W., Gatzy, J., Dalton, Ch., 1961, Studies on the equilibration of mercury vapor with blood. The University of Rochester, Atomic Energy Project, report nr. UR-582.Google Scholar