Abstract 16527: Gender Differences in Salt Sensitivity to Nitric Oxide-Dependent Vasodilation in Healthy Young Adults
Salt sensitivity may be associated with endothelial production of nitric oxide (NO). We therefore tested the hypothesis that dietary sodium influences the NO component of endothelium-dependent vasodilation in young adults. We measured forearm blood flow (FBF, plethysmography) responses to brachial artery administration of acetylcholine (ACh, 4 mcg/100 ml tissue/min) before and after endothelial NO synthase inhibition with NG-monomethyl-L-arginine (L-NMMA, 50 mg bolus + 1 mg/min infusion). Studies were conducted after 5 days of a controlled calorie, protein, potassium, calcium, and high sodium (400mmol/day) diet, and compared to data from an identical protocol in our laboratory after 5 days of sodium restriction (10 mmol/day). Individuals in the low (n = 30, mean age ± SEM = 30 ± 1 yr, 16 men) and high sodium (n = 36, age 23 ± 1 yr, 13 men) groups were healthy, lean, and normotensive. After low sodium, ACh increased FBF from 2.8 ± 0.2 at baseline to 19.5 ± 1.9 ml/100ml/min (P<0.001). L-NMMA decreased resting FBF to 1.7 ± 0.1 (P<0.001 from baseline); ACh then increased FBF to 12.7 ± 1.6 (P<0.001). After high sodium, ACh increased FBF from 3.2 ± 0.3 at baseline to 19.3 ± 1.4 (P<0.001). L-NMMA decreased resting FBF to 1.7 ± 0.1 (P<0.001 from baseline); ACh then increased FBF to 15.3 ± 1.3 (P<0.001). To quantify the NO component of endothelium-dependent dilation we compared the vasodilator responses to ACh before and after L-NMMA accounting for changes in baseline FBF caused by L-NMMA: [(FBF AChL-NMMA - FBF baselineL-NMMA) - (FBF ACh - FBF baseline)]. This value was -5.7 ± 1.3 and -2.5 ± 0.8 ml/100 ml forearm tissue/min for the low and high sodium diets, respectively (P = 0.03). This difference was driven by the men, with values of -7.9 ± 2.0 and -2.2 ± 1.4 observed (P=0.03) versus -3.1 ± 1.3 and -2.7 ± 1.0 for the women (P = 0.8). Thus, the vasodilator response to ACh was not affected by the diets, but in men the NO component was higher following sodium restriction and lower after high sodium, with no diet-based differences observed in women. These observations suggest that endothelial NO production is sensitive to extremes of sodium intake in healthy young men but not women.
- © 2011 by American Heart Association, Inc.