Abstract
In earlier communications 1 we reported the oxidation of lactic to pyruvic acid and hemoglobin to methemoglobin by normal dog erythrocytes in the presence of 0.005% methylene blue. Pyruvic acid is not further oxidized. Because the oxygen partition seemed to indicate coupled reactions, it was tentatively suggested that the mechanism was one of peroxidation. Further studies, in which the stochiometric relationships observed with sugar-free cells were not obtained in presence of glucose, led us to question the explanation first offered.
Warburg, Kubowitz and Christian 2 explain methylene blue catalysis in red blood cells by the following chain of reactions: (a) oxidation of hemoglobin to methemoglobin by methylene blue; (b) oxidation of carbohydrate (or derivative) by methemoglobin with regeneration of hemoglobin; (c) oxidation of leuco-methylene blue by O2. (A detailed paper by Warburg et al 3 which reached us while writing this report appears to substantiate their earlier interpretation.)
If methemoglobin is the agent responsible for methylene blue catalysis in red blood cells, it should be possible to oxidize lactic acid with methemoglobinized cells in the absence of O2. And if no other oxidations occur, an equivalent amount of hemoglobin should be formed, as follows:
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