Effects of sodium intake on the presser and renal responses to nitric oxide synthesis inhibition in normotensive individuals with different sodium sensitivity

Objective The present study evaluated the role of nitric oxide (NO) in the systemic vascular and renal adaptation to changes in dietary sodium intake. Design and methods Seven healthy normotensive male subjects were randomized to high or low sodium diets in a double blind crossover design (7 days on each diet). The NO synthesis inhibitor, N(G)monomethyl-L-arginine (L-NMMA) was infused systemically (1.8 mg/kg over 30 min) at the end of each dietary period and its effects on blood pressure, renal plasma flow, glomerular fi ltration rate, urinary flow rate and sodium excretion were measured. Results Blood pressure increased in response to L-NMMA on a high sodium die t only (area under time curve percentage change in mean blood pressure, low sodium = -94.5 +/- 164.3; high sodium = 391.1 +/- 228.6; P< 0.05 low versu s high). The increase in blood pressure was directly and significantly asso ciated with the individual salt sensitivity, defined by the difference in s ystemic mean blood pressure between high and low sodium diets (r = 0.756; P < 0.05). L-NMMA also reduced renal plasma flow and urinary flow rate in sub jects on high sodium diet Conclusions The data support a significant influence of endogenous NO in th e systemic and renal vascular adaptation to a high sodium diet in normotens ive men. In addition, the direct association between the individual sodium- sensitivity and the presser response to L-NMMA suggests that there is incre ased dependence of vascular tone on NO in normotensive subjects whose blood pressure is more sodium sensitive. I Hypertens 2000, 18:615-621 (C) Lippin cott Williams & Wilkins.