Dietary L-arginine supplementation improves the glomerular filtration rate and renal blood flow after 24 hours of unilateral ureteral obstruction in rats.

PURPOSE: Unilateral ureteral obstruction (UUO) results in a significant change in renal blood flow (RBF) and glomerular filtration rate (GFR) by 24 hours. The intake of L-arginine, a substrate of nitric oxide (NO) synthase (NOS), can augment NO production. NO can maintain renal function through its vasodilatory action. Therefore, we examined the effect of dietary arginine supplementation on renal function in UUO.

MATERIALS AND METHODS: GFR and RBF were measured by inulin and para-aminohippurate clearance, respectively, in control rats and in rats 24 hours after UUO. Rats were given arginine with or without the concomitant administration of N-nitro-L-arginine methyl ester. Urinary nitrate/nitrite (NO2/NO3) was measured by the Griess reaction and urinary cyclic guanosine monophosphate was determined by enzyme-linked immunosorbent assay. The expression of renal inducible NOS was determined by immunohistochemistry.

RESULTS: Urinary NO2/NO3 was significantly increased after 2 weeks of arginine, confirming increased NO production. In control rats GFR and RBF were not significantly different in untreated vs arginine treated groups. In contrast, arginine treatment significantly increased GFR in the obstructed kidney (0.06 +/- 0.01 to 0.14 +/- 0.02 ml per minute per 100 gm) and the contralateral kidney compared with control UUO. RBF was also significantly increased by arginine. The increases in renal function with arginine were blunted by a NOS inhibitor in obstructed and contralateral kidneys. Inducible NOS expression was increased in obstructed and contralateral kidneys.

CONCLUSIONS: This study demonstrates that L-arginine supplementation can improve renal function in acute UUO. This finding suggests that NO system may be a future site of pharmacological intervention for UUO.