Sodium chloride loading does not alter endothelium-dependent vasodilation of forearm vasculature in either salt-sensitive or salt-resistant patients with essential hypertension

The purpose of this study was to determine whether a high NaCl intake impairs endothelium-dependent and -independent vasodilation of forearm circulation in salt sensitive (SS) patients with essential hypertension. We evaluated the effects of intra-arterial acetylcholine (ACh) and isosorbide dinitrate (ISDN) on forearm hemodynamics in 29 patients with essential hypertension, while consuming a low NaCl (50 mmol/d) or high Na Cl (340 mmol/d) diet for 1 week. The forearm blood flow (FBF) was measured by strain-gauge plethysmography. Patients were classified as SS (n=12) or salt resistant (SR; n=17) based on salt-induced changes in blood pressures. The FBF responses of ACh and ISDN were similar in the SS and SR patients while on either NaCl diet, and was not altered by salt loading (ACh, SS: low NaCl 22.8 +/-4.3 vs. high NaCl 21.1 +/-3.6 ml/min per 100 ml, SR: low NaCl 22.5 +/-4.0 vs. high NaCl 23.3 +/-4.1 ml/min per 100 ml; ISDN, SS: low NaCl 13.9 +/-2.1 vs. high NaCl 14.1 +/-2.2 ml/min per 100 ml, SR: low NaCl 13.8 +/-2.3 vs. high NaCl 14.0 +/-2.2 ml/min per 100 mi). There were no significant differences in the vascular responses to ACh and ISDN in the presence of N-G-monomethyl-L-arginine, a nitric oxide synthase inhibitor, in either group for either NaCl diet. These findings suggest that forearm resistance artery endothelial function may not be influenced by salt loading in either SS patients which finding may play a role in determining salt sensitivity in patients with essential hypertension or SR patients.