Begrenzende Faktoren der Methämoglobinbildung durch Phenylhydroxylamin in Hämolysaten verschiedener Tierarten

Summary

1. Addition of ATP, G-6-P, G-6-PDH and NADP to haemolysates of erythroyctes from pigs, cows, and sheep increased the formation of methaemoglobin through phenylhydroxylamine by various degrees, according to the animal source used. The results revealed limiting factors for the formation of methaemoglobin in haemolysates. These factors are compared with the limiting factors found in intact erythrocytes.

2. Phosphorylation of glucose limits NADP reduction and, consequently, the methaemoglobin formation in haemolysates of erythrocytes from the three animals. The individual limiting factors are as follows: in sheep erythrocytes, the activity of hexokinase; in pig erythrocytes, the glucose utilisation; in cow erythrocytes, the ATP concentration.

3. When the hexokinase reaction is circumvented by the addition of G-6-P, the activity of NADPH-diaphorase limits the formation of methaemoglobin in the haemolysates of cow erythrocytes. However, the formation of methaemoglobin in haemolysates of pigs and cows can be increased by the addition of NADP before the activity of diaphorase becomes the limiting factor.

4. After adding a complete NADPH regenerating system, the velocities of methaemoglobin formation in haemolysates from the three animals were found to correlate with the corresponding disphorase activities.