Glucose oxidation in rat brain slices and homogenates

Abstract

With the aid of C 14-labeling, various glycolytic and respiratory properties of rat brain preparations were studied. Glucose oxidation as well as glycolysis occurred readily in isotonic whole brain homogenates, fortified with ATP and DPN. Under optimal conditions glucose oxidation accounted for about 60 per cent of the total respiration. Added TPN markedly enhanced the oxidation of glucose carbon-1 but had no effect on the oxidation of other glucose carbons. In short-term experiments conducted over a wide glucose concentration range, glucose oxidation in homogenates was almost maximal at 0.0002 M, whereas in slices, maximal oxidation was reached at 0.001 M. Fructose-U-C 14 was readily oxidized by brain slices, but its oxidation was almost completely inhibited in the presence of glucose. Comparison of the radioactivity of lactic acid formed in brain slices and homogenates from glucose-1-C 14 and glucose-U-C 14 indicated the essential exclusive occurrence of the Embden-Meyerhof process. Although some glucose oxidation was observed with isolated brain mitochondria, it appeared this was due to contaminating cytoplasm, since glucose oxidation was greatly enhanced by the addition of the supernatant fraction.