Acute dietary salt loading impairs cutaneous microvascular function in normotensive salt‐resistant adults: role of oxidative stress

Abstract

Animal studies have reported dietary salt‐induced reductions in vascular function without an increase in blood pressure (BP). The purpose of this study was to determine if acute dietary salt loading impairs cutaneous microvascular function in normotensive adults with salt‐resistant BP. Following a control run‐in diet, 10 normotensive salt‐resistant subjects (31±3 yr) were randomized to a 7 day high salt (HS; 350 mmol/day) and 7 day low salt (LS; 20 mmol/day) diet (controlled feeding study). Salt‐resistant BP was defined as a change in 24‐hour mean BP of ≤ 5 mmHg from the LS to the HS diet. On the last day of each diet, subjects were instrumented with three microdialysis fibers for the local delivery of Ringer's solution (R), 10 mM L‐NAME, and 20 mM ascorbic acid (AA). Laser Doppler flowmetry was used to measure red blood cell flux during local heating (42□). All data were expressed as a percentage of the maximum cutaneous vascular conductance (CVC) at each site (28 mM SNP; 43□). The plateau %CVCmax was reduced during HS (LS 93±1 v. HS 80±2, P<0.05), as was the nitric oxide (NO) contribution to the plateau (LS 55±5 v. HS 46±3, P=0.075). During HS, AA improved the plateau %CVCmax (R 80±2 v. AA 89±3, P<0.05) and restored the NO contribution (R 46±3 v. AA 60±7, P<0.05). These data suggest that acute dietary salt loading impairs cutaneous microvascular function in normotensive salt‐resistant adults and indicate a role for oxidative stress.Supported by 2 P20 RR016472‐11 and HL104106.