The metabolism of lactic and pyruvic acids in normal and tumour tissues

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Abstract
In neither of these tissues does the metabolism follow the cycle found in kidney cortex. In retina, lactate and pyruvate are oxidized quite rapidly. Succinate is oxidized slightly to fumarate and there is an equilibrium between fumarate and malate but no further oxidation. Fumarate causes an unexplained lowering of the R.Q. Acetate, formate, B-oxybutyrate, citrate, and a-ketoglutarate are not oxidized to any extent. Like liver, brain and testis, retina shows a much higher rate of aerobic glycolysis during the first few minutes equilibration than in the experimental period. Manometric work shows that some acid intermediate other than pyruvate is formed from lactate during the first stage of oxidation, and later, when lactate is no longer oxidized, the unknown acid acts as substrate. In embryo, added lactate and pyruvate are metabolized to some extent. Succinate. fumarate, malate, a-ketoglutarate and citrate are not attacked. The coarsely chopped tissue shows no fumarase activity. Oxalate is oxidized. The results in this series of papers are discussed in relation to the theories of Szent-Gyorgyi and Krebs.