Abstract 425.

Background: High dietary sodium (Na) intake has been shown to be related to the development of endothelial dysfunction and hypertension. Urinary sodium excretion in people with normal renal function can indirectly reflect the level of dietary sodium intake. The purpose of the study was to test whether high urine Na excretion was independent from other risk factors and related to the compromised endothelial-dependent (fiow-mediated dilation [FMD]) and/or endothelium-independent (nitroglycerin-induced dilation [NMD]) in normotensive African Americans. Normotensives were studied in order to eliminate the influence of hypertension.METHODS: Urine was collected for 24 hr in 30 subjects aged 41-63 yrs with normal blood pressure (125.7 ± 9.7/81 ± 7.1 mmHg). 16 subjects had Na excretion <150 mmol (99.6 ± 24.8 mmol) and were classified as the Normal Na excretion group and 14 subjects had Na excretion ≥150 mmol/g (186.5 ± 27.1 mmol) and were classified as the High Na excretion group. FMD was measured after 5-min cuff occlusion and NMD was measured after application of 0.8 mg nitroglycerin using Doppler ultrasound. The maximum FMD- and NMD-diameters and FMD/NMD ratio were calculated.Results: There were no differences in other dietary factors, age, body mass index, blood pressure, or physical activity levels between the groups. Plasma concentrations of cholesterol, glucose, antioxidant status and inflammatory markers did not differ between groups. FMD (Normal: 7.4 ± 2.9% vs. High: 9.5 ± 3.6%; p=0.09) and NMD (Normal: 17.9 ± 6.3% vs. High: 27.8 ± 18.1%; p=0.07) and true peak FMD/NMD ratio (Normal: 0.45 ± 0.22 vs. High: 0.38 ± 0.11; p=0.26) were not different between groups. No significant correlations were found between 24hr Na excretion and FMD (r=0.332; p=0.073), NMD (r=0.356; p=0.053) or FMD/NMD ratio(r=0.112; p=0.554) in the entire study group.Conclusion: High Na excretion was not associated with reduced endothelial responsiveness in healthy African Americans with normal blood pressure. These results suggest that high Na intake may not be predictive of endothelial dysfunction in putatively healthy populations. [ABSTRACT FROM AUTHOR]