Methämoglobinbildung in Erythrocyten durch Peroxideinwirkung. Versuche zur Beurteilung der Schutzfunktion von Katalase und Glutathionperoxidase

Abstract

The rate of methaemoglobin formation induced by small amounts of H2O2, a) generated enzymatically, or (b) added by diffusion as vapour, has been investigated in suspensions of normal and acatalasic red cells. At low rates of H2O2‐generation (i.e. 10−10−10−9 moles H2O2/mg Hgb/min) removal of H2O2 is mainly due to glutathione peroxidase activity, whereas at higher rates (i.e. 10−9−10−7 moles H2O2/mg Hgb/min) catalase activity is responsible for haemoglobin protection. Under the latter experimental conditions the yield of methaemoglobin formcd depends mainly on red cell catalase activity. The existence of a lag‐phase in methaemoglobin formation and measurements of reduced glutathione concentration suggest that catalase and haemoglobin compete for excess H2O2 only after the intracellular supply of reduced glutathione has been exhausted and the H2O2 concentration in the cells has passed a critical level of than 7 · 10−6MH2O2.

Oxidative stress and protective mechanisms in erythrocytes in relation to Plasmodium vinckei load.

“…The possibility that the cytosolic compartment of the PRBC is under oxidative stress remains open. Several authors (28,29) have argued that the hemoglobin present within intact RBC is protected against oxidation by H202 as long as GSH is available as an electron donor for GSH peroxidase. When GSH is oxidized faster than it can be regenerated, catalase and hemoglobin compete for the excess H202 and formation of methemoglobin can occur.…”