Studies on carbohydrate metabolism in rat liver slices. VIII. Effect of ions and hormones on pathways of glucose-6-phosphate metabolism.

Our present knowledge of carbohydrate metabolism requires that glucose must first be phosphorylated before undergoing further metabolism. Once phosphorylated to glucoseS-phosphate, at least four pathways of metabolism are available. Glucose-6-phosphate may be (1) converted to glucosel-phosphate, from which glycogen and other polysaccharides arise, (2) hydrolyzed to glucose and inorganic phosphate, (3) metabolized via the Embden-Meyerhof pathway, or (4) metabolized via the phosphogluconate oxidation pathway. However, it should be pointed out that all of these pathways of metabolism are not found in all mammalian tissues. For example, muscle contains no glucose-6-phosphatase and little glucose-6phosphate dehydrogenase; therefore pathways (2) and (4) are not available in this tissue. In liver, all four pathways of glucose-6-phosphate metabolism do exist. Our present purpose is to evaluate the relative rates of these four pathways in liver slices from normal and alloxan-diabetic rats. In addition, the effects of sodium and potassium ions on the metabolism of glucoseS-phosphate in vi&o were studied by incubating liver slices from normal rats in media of varying ionic composition.