INCREASES IN NO2-/NO3- EXCRETION IN THE URINE AS AN INDICATOR OF THE RELEASE OF ENDOTHELIUM-DERIVED RELAXING FACTOR DURING ELEVATION OF BLOOD-PRESSURE

1. Under hormonally constant conditions, the effects of a sudden increase in blood pressure on the release of endothelium-derived relaxing factor were evaluated by measuring urinary excretion of NO2-/NO3- in rats with renal denervation. 2. Elevation of blood pressure from 136 +/- 2 to 153 +/- 3 mmHg by an aortic clamp below the renal arteries induced a significant increase in urinary excretion of NO2-/NO3- from 76.6 +/- 4.2 x 10(2) to 108.1 +/- 8.3 x 1O(2) pmol min-1 g-1 kidney weight (P<0.05). 3. Infusion of N(G)-monomethyl-L-arginine (1 mg min kg-1) without an aortic clamp raised mean blood pressure to a similar level; however, urinary excretion of NO2-/NO3-was decreased significantly. 4. During infusion of N(G)-monomethyl-L-arginine, aortic occlusion caused a significant increase in blood pressure without any changes in NO2-/NO3- excretion in the urine. 5. These results suggest that the formation of NO, an indicator of endothelium-derived relaxing factor release, was increased by mechanical pressure elevation without apparent changes in hormonal and neural factors.