Renal response during acute unilateral ureteral obstruction in rats

The early renal response to unilateral ureteral occlusion (UUO) and its mec hanism have been extensively studied in dogs but seldom discussed in the mo st frequently used laboratory animals, rats. The acute phase of the renal r esponse to UUO was studied in female rats weighing 190-236 g. We recorded t he ureteral pressure and changes in renal parameters throughout 120 minutes of UUO in control (US, UUO + saline, n = 10), L-arginine-treated (UA, n = 10), and right-nephrectomized rats (UO, UUO in one kidney, n = 9). Ureteral pressure increased in all three groups of rats after complete ureteral obs truction. The extent of the increase was not significantly different betwee n US and UA rats but was significantly higher in the UO rats. In US rats, t he cortical microvascular blood now (CMVBF), measured by a laser Doppler fl owmeter, declined significantly, from 321 +/- 10 perfusion units (PU) to 26 0 +/- 11 PU. The percentage of drop in CMVBF at 120 minutes of UUO was sign ificantly greater in UO (25.7 +/- 3.8%) than in US (19 +/- 2.1%) and in UA (14 +/- 2%) rats. Acute UUO reduced the glomerular filtration rate (GFR) in US and UO rats, whereas L-arginine attenuated this decrease. The excretion of nitrate/nitrite was increased after UUO. Giving NG-nitro-L-arginine met hyl ester hydrochloride (L-NAME, 12 mg/kg/h) during UUO did not reduce CMVB F more severely. Western blot analysis of endothelial nitric oxide synthase expression in the renal cortex and medulla protein extracts revealed no di fferences between US and sham-operated rats. Acute UUO did not lead to rena l hyperemia in rats. Reduction of nitric oxide during UUO might contribute to the decrease of renal circulation during UUO. Neurourol. Urodynam. 20:12 5-137, 2001. (C) 2001 Wiley-Liss. Inc.