Metabolism of C¹⁴- labeled substrates in kidney cortical slices from normal and alloxan-diabetic rats

¹ Departments of Medicine, Harvard Medical School and Peter Bent Brigham Hospital; and Baker Clinic Research Laboratory, New England Deaconess Hospital, Boston, Massachusetts

The metabolism of C¹⁴-labeled glucose, fructose, mannose and pyruvate was studied in kidney slices from normal and alloxan-diabetic rats. Labeled carbon was recovered in CO₂, glycogen and fatty acids. The rate of mannose metabolism was consistently slightly less than that of glucose, and on the other hand, the rate of fructose metabolism was consistently greater. In slices from alloxan-diabetic animals the metabolism of glucose and mannose was markedly reduced; that of fructose was only slightly decreased. No effect of insulin added in vitro could be demonstrated on glucose metabolism. Pyruvate oxidation to CO₂ was slightly increased in slices from diabetic animals. Furthermore, glucose production was increased sixfold by diabetes and, as calculated, 75% of this glucose production could be accounted for by glucose synthesized from labeled pyruvate. The similarity between carbohydrate metabolism in liver and kidney was pointed out.