Inhibition of glucose reabsorption induced by 6-aminonicotinamide in the rat kidney.

Abstract

The relationship between natriuresis and glucosuria produced by administration of 6-aminonicotinamide (6-AN), was investigated in the rat. After intraperitoneal administration of 6-AN (75 mg/kg), urine was collected at intervals of 2 hours using a metabolic cage for assays. Sodium and glucose were excreted maximally into the urine at 2 to 4 and at 4 to 6 hours, respectively, after the administration of 6-AN, with a time delay being recognized between sodium and glucose in the peaks of their urinary excretions. This dissociation of the patterns on the urinary excretion between sodium and glucose led to the following conclusion that the natridiuresis induced by 6-AN was not mainly ascribed to the osmotic diuresis for glucose, but to the direct effect on the sodium transport in the kidney. Furthermore, additional experiments were carried out by loading animals with glucose after administration of 6-AN. The tolerance for glucose in the body was clearly depressed in rats in the 6-AN group, while no significant difference in the renal threshold concentration for glucose was shown in either group. The renal tubular transport maximum for glucose was also depressed in the 6-AN group. It is, accordingly, speculated that the glucosuria induced by 6-AN was not only due to the hyperglycemia, but also due to the decreased capacity of the renal tubular reabsorption for glucose.