Distribution of glucose and related metabolites in rat kidney

Abstract

The distribution of glu-cose and related metabolites were measured in the renal cortex and medulla of anesthetized rats. A glucose gradient was observed with highest levels in the outer cortex and lowest in inner medulla. A 3-fold glycogen gradient was found running in the opposite direction to the glucose gradient. ATP, and creatine-P were uniformly distributed. Lactate levels were low with medullary levels slightly higher than cortical levels. Phlorizin greatly increased medullary glucose reversing the normal gradient; glucose loading increased glucose concentration in all layers, but no changes in glycogen, ATP, creatine-P, or lactate occurred. The diuretics chlorothiazide and mercaptomerin produced no significant alterations of the metabolites measured. Cutting off the blood supply to the kidney resulted in a precipitous fall in cortical ATP, whereas in the medulla the fall was much slower, apparently due to the higher rate of glycolysis. In alloxan-diabetic rats, hyperglycemia was associated with high renal glucose, glycogen and glucose-6-P concentrations, whereas in insulin-treated rats the hypoglycemia was accompanied by markedly depressed glucose levels in cortex and medulla, and depressed glycogen levels in medulla only.