Role of Inducible Nitric Oxide Synthase as a Mediator of Renal Ischemia/Reperfusion Injury in the Rat

Moon, Ki Hak; Cho, Chul Kyu; Jung, Hee Chang; Park, Tong Choon; Choi, Hyung Chul; Kim, Yong Jin; Choi, Tae Soo

Abstract

PURPOSE: This study was undertaken to elucidate if nitric oxide (NO), produced by inducible nitric oxide synthase (iNOS) following renal ischemia/reperfusion (I/R), contributes to renal injury in rats, and if selective inhibition of iNOS prevents tissue injury following I/R.
MATERIALS AND METHODS
Sprague-Dawley rats (male, 200-250gm, n=80) were divided into 4 groups. The groups were pretreated with L-arginine (L-ARG group), N-nitro-L- arginine methyl ester (L-NAME group), aminoguanidine (AG group) or normal saline (control group) before I/R. The renal blood flow was measured using laser Doppler at the left renal pedicle just before clamping the pedicle and at 15, 30, and 45 min after reperfusion. The HandE stain of nephrectomized tissues following I/R was performed for histological scoring of tubular damage and medullary vascular congestion. The expression of iNOS, using reverse transcription-polymerase chain reaction (RT-PCR), in the AG and control groups was determined in the kidney tissues following I/R.
RESULTS
The recovery rate of the renal blood flow after I/R was significantly higher in the AG group compared to the controls. From light microscopy, the control group showed attenuated tubular lining epithelial cells, especially in the proximal tubules. However, Glomeruli and individual tubular cells showed no pathological changes. Mild congestion was noted in the medullary area. The L-NAME group showed marked tubular necrosis and medullary congestion. This tubular necrotic injury was compromised in the L-ARG group, but it was almost normal in the AG group. The medullary congestion was still severe in the L-ARG group, but was minimally present in the AG group. RT-PCR of the iNOS in the rat renal tissue revealed an iNOS band at 200bp. No significant difference in the density of the iNOS band was observed between the two groups.
CONCLUSIONS
These results suggest that the NO, produced by iNOS following I/R, leads to renal tubular necrosis and medullary congestion, and selective inhibition of the iNOS may prevent renal tissue damage following I/R injury.