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

1 The rate of methaemoglobin formation induced by small amounts of H 2 O 2 , a) generated enzymatically, or (b) added by diffusion as vapour, has been investigated in suspensions of normal and acatalasic red cells. 2 At low rates of H 2 O 2 ‐generation ( i . e . 10 −10 −10 −9 moles H 2 O 2 /mg Hgb/min) removal of H 2 O 2 is mainly due to glutathione peroxidase activity, whereas at higher rates ( i . e . 10 −9 −10 −7 moles H 2 O 2 /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. 3 The existence of a lag‐phase in methaemoglobin formation and measurements of reduced glutathione concentration suggest that catalase and haemoglobin compete for excess H 2 O 2 only after the intracellular supply of reduced glutathione has been exhausted and the H 2 O 2 concentration in the cells has passed a critical level of than 7 · 10 −6 M H 2 O 2 .