Renal conversion of fructose to glucose

Abstract

Aspects of renal metabolism of fructose have been studied in rats without interference from the liver but without hypoglycemia. Data were obtained which suggest that added renal venous glucose found after injection of fructose arose nearly quantitatively from fructose. The decrease in concentration of fructose or increase of glucose on passage of blood through the kidney permitted calculation of a clearance value closely similar to the inulin/Diodrast clearance fraction of rats, suggesting that conversion of fructose to glucose may be a process connected with tubular transport. Randomization of radioactivity during conversion of fructose-6-C¹⁴ led to appreciable accumulation of label in C-1 of renal venous glucose. This was analogous to events during intestinal transport of fructose in guinea pigs, which had been shown to be caused by intermediate scission into three carbon units. A similar mechanism thus may operate in renal tissue of rats. Glomerular filtration seemed to persist after ureteral ligation, tending to explain persistence of conversion of fructose to glucose at a reduced level. No appreciable net contribution of glucose to blood by the kidney was found when no injections were given or when saline alone was administered.