Effects of dietary nitrate supplementation on NO‐mediated vasodilation during local heating in healthy humans

Abstract

Nitrate supplementation in the form of beetroot juice (BRJ) has been shown to increase NO where nitrate can be converted to nitrite and NO through both NOS‐independent and dependent pathways. We hypothesized BRJ would augment the NO‐dependent component of cutaneous thermal hyperemia. Six subjects were equipped with two microdialysis fibers on the forearm and randomly assigned to lactated Ringer's (control) or 20mM L‐NAME (NOS inhibitor). Site 1 was perfused with LNAME once a plateau in the local heating response was achieved to quantify NO‐dependent vasodilation. Skin blood flow via laser‐Doppler flowmetry (LDF) and mean arterial pressure were measured; cutaneous vascular conductance (CVC) was calculated as LDF/MAP and normalized to %CVCmax. Subjects reported to the lab for pre‐and post‐supplement local heating protocols. Dietary intervention consisted of 1 shot of BRJ (.45g nitrates; 5mM) for 3 days. There was no significant difference between %NO contribution to local heating pre‐BRJ (60 ± 4 %CVCmax) and post‐BRJ (63% ± 2 %CVCmax) supplementation. These data suggest BRJ does not improve NO‐mediated vasodilation in the cutaneous vasculature in response to local heating in healthy humans.