Oxidation of Lactic Acid by Dog Erythrocytes.

Abstract

The blood of certain species converts glucose to lactic acid but lacks the power of oxidizing either, and of oxygen consumption. The observation by Fürth and Lieben of lactic acid destruction by horse erythrocytes was not confirmed by Warkany; while Koechig in this laboratory using the method described by Ray failed to detect loss of lactate or formation of acetaldehyde. It appears that such “activation” of glucose as occurs in glycolysis does not alone suffice to accomplish the oxidation either of glucose or lactic acid—or an intermediate—by molecular oxygen. The same inference can be drawn from the similar behavior of cancer tissue or muscle extracts, the glycolyzing power of which is little affected by oxygen (Warburg and Meyerhof). Recently Barron and Harrop have shown that the addition of methylene blue to blood undergoing glycolysis causes a marked change in its behavior. There results an increase of O2 consumption and of CO2 production, and a large part of the sugar which disappears fails to appear as lactic acid, thus resembling reactions observed with muscle and other tissues. In the presence of the dye the blood respires with the oxidation, presumably, of either glucose or lactic acid or both. The rate of sugar disappearance is only slightly affected. The dye appears to supply an oxidation catalyst of a sort which is normally absent. We have confirmed the observations of Barron and Harrop cited above and have attempted to decide whether it is the glucose which is oxidized and thus prevented from appearing as lactic acid, or whether lactic acid may be first formed and subsequently oxidized. Our results show that dl-sodium lactate added to washed blood erythrocytes disappears on incubation in air in the presence, but not in the absence of methylene blue.