Role of endothelium-derived nitric oxide in hemodynamic adaptations after graded renal mass reduction.

The mediator(s) of the adaptive increases in renal blood flow (RBF) and glomerular filtration rate (GFR) after renal mass reduction have not been identified. The present studies were designed to investigate the role of endothelium-derived nitric oxide (EDNO) in the hemodynamic adaptations after graded renal mass reduction. The experiments were performed in rats that had undergone a sham reduction in renal mass, uninephrectomy (UNX), or 5/6 NX (UNX plus excision of both poles of the contralateral kidney) 3-4 wk before. Measurements of RBF, GFR, renal vascular resistance (RVR), mean arterial pressure (MAP), and plasma renin concentration (PRC) were obtained before and after administration of the EDNO synthesis inhibitor NG-monomethyl-L-arginine (L-NMMA). L-NMMA (50 mg/kg bolus plus 500 micrograms.kg-1.min-1 infusion) led to significant (P < 0.01) and comparable increases in MAP (mmHg) (P < 0.01) in sham rats (117 +/- 6 to 154 +/- 6), UNX rats (112 +/- 5 to 139 +/- 7), and 5/6 NX rats (116 +/- 5 to 149 +/- 7). RVR increased significantly in all three groups (P < 0.01). The resultant decrease in RBF (ml.min-1.kg-1) was similar in sham rats (34.9 +/- 2.6 to 23.8 +/- 1.6), UNX rats (43.9 +/- 3.6 to 27.3 +/- 2.8), and 5/6 NX rats (34.6 +/- 2 to 22.3 +/- 1.6) (P < 0.01 for all groups).(ABSTRACT TRUNCATED AT 250 WORDS)