Metabolism of dog gastric mucosa. Levels of glycolytic, citric acid cycle and other intermediates.

Several metabolites, including those of glycolysis, the citric acid cycle, the hexose monophosphate shunt, glutamate, aspartate, and Coenzyme A were measured in defined parietal cell-enriched freeze-dried sections of dog gastric biopsies derived from nonsecreting and secreting tissue. In addition, NH3, ribulose 5-phosphate, glycerol, and succinate were measured in perchloric acid extracts of biopsies. The onset of secretion increased the level of glycolytic intermediates including pyruvate and lactate with the most marked increase being in fructose 1,6-diphosphate levels. The level of 6-phosphogluconate and ribulose 5-phosphate also increased, in spite of a constant NADP+/NADPH ratio. The levels of all the citric acid cycle intermediates measured also rose, the most marked rise being in malate and fumarate. The levels of glycerol, acetyl-CoA, and CoA increased, but the ratio of the latter intermediates remained constant. Calculation of the ratio of the oxidized to reduced form of diphosphopyridine nucleotide indicated a fall of the ratio in the cytoplasm and a rise in the mitochondria. From these data, it is concluded that the major energy source for acid secretion is due to an increase in citric acid cycle activity and that glycolysis, and probably also fatty acid oxidation, is stimulated to provide mitochondrial substrate.