To assess the renal haemodynamic response to manipulations of the nitric oxide (NO) system, we examined subtotally nephrectomized (SNX) rats and control rats (CON) 28 days after their operation. Bolus infusions of the NO synthase inhibitor NG-nitro-L-arginine (L-NA) were given intravenously at doses of 2 mg/kg and 10 mg/kg. Blood pressure was measured intra-arterially, glomerular filtration rate was measured by inulin clearance and fractional changes in renal blood flow (RBF) were determined by a Doppler flow probe. Both doses of L-NA caused a similar and dose-dependent increase in mean blood pressure in both SNX and CON rats. In contrast, the decrease in RBF and the increase in the renovascular resistance index (RVRI) was less in SNX rats as compared to CON rats (RBF = -70.1 +/- 2.2% of baseline vs -52.7 +/- 5.2%, P < 0.01; RVRI = +177 +/- 9% of baseline vs +243 +/- 24%, P < 0.05). These changes were not affected by autonomic blockade (hexamethonium), or by blockade of the angiotensin II receptor (Losartan). The exogenous NO donor sodium nitroprusside (0.5 and 1.5 micrograms.kg-1.min-1) lowered mean blood pressure to a similar degree in SNX and CON rats; in contrast, RVRI decreased less in SNX rats (86.9 +/- 9.2% of baseline) than in CON rats (68.2 +/- 4.6%, P < 0.05). We conclude that the reaction of the renal vasculature to manipulations of the NO system is altered in the SNX rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Amino Acid Oxidoreductases Animals