Salt-induced increase in arterial pressure during nitric oxide synthesis inhibition.

The objective of this study was to determine in conscious dogs the role of endothelium-derived nitric oxide in mediating the arterial pressure and renal response to a prolonged increment of sodium intake. After a control period of 3 days, an inhibitor of nitric oxide synthesis, NG-nitro-L-arginine-methyl ester, was infused intravenously during 5 consecutive days (0.1 micrograms/kg per minute). Sodium intake (80 mmol/d) did not change throughout the experiment in one group (n = 4). In another group (n = 6), 1 day after infusion of this inhibitor was started, sodium intake increased from 80 to 300 mmol/d during 4 consecutive days. Inhibition of nitric oxide synthesis in dogs with normal sodium intake induced a significant decrease in natriuresis and diuresis (P < .05) without changes in arterial pressure. However, in dogs treated with the nitric oxide synthesis inhibitor, mean arterial pressure increased from 95.2 +/- 3.3 to 106.2 +/- 4.0 mm Hg (P < .01) the first day that sodium intake was elevated and remained increased the following 3 days. In a different group of dogs (n = 5), the increment of sodium intake during 4 days did not induce changes in arterial pressure when nitric oxide synthesis was not inhibited. Cumulative sodium balance was higher (P < .01) in dogs treated simultaneously with the nitric oxide synthesis inhibitor and high sodium intake (158 +/- 21 mmol sodium) than in those treated only with the nitric oxide synthesis inhibitor (82 +/- 19 mmol sodium) or with high sodium intake (36 +/- 13 mmol sodium).(ABSTRACT TRUNCATED AT 250 WORDS)