Local arginase inhibition and low-dose sodium nitroprusside administration do not modulate heat loss responses in young and older men during exercise

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Title: Local arginase inhibition and low-dose sodium nitroprusside administration do not modulate heat loss responses in young and older men during exercise
Authors: Meade, Robert
Fujii, Naoto
McGarr, Gregory
Alexander, Lacy
Boulay, Pierre
Sigal, Ronald
Kenny, Glen
Date: 2019
Abstract: Age-related impairments in cutaneous vasodilation and sweating may result from increased arginase activity (which can attenuate endogenous NO production), and/or altered NO sensitivity of the thermoregulatory end-organs (i.e., cutaneous vasculature and sweat gland). We evaluated whether local arginase inhibition or low-dose sodium nitroprusside (SNP; NO donor) modulate cutaneous vascular conductance (CVC) and sweat rate (SR) in young (n=9, 23±3 years) and older (n=9, 66±6 years) men during an exercise-heat stress. We also assessed the influence of these treatments during whole-body passive heating in older men (n=7, 64±7 years). During two 30-min bouts of moderate-intensity cycling (Ex1 and Ex2) in the heat (35˚C), CVC and SR were measured at forearm skin sites perfused with: 1) lactated Ringer’s (Control); 2) 5mM Nω-hydroxy-nor-Arginine + 5mM S-(2-boronoethyl)-L-cysteine (Nor-NOHA+BEC, arginase-inhibited); or 3) 1µM SNP. The influence of these treatments on CVC and SR was also evaluated at passively-induced elevations in esophageal temperature (∆Tes) equal to those in Ex1 (0.6°C) and Ex2 (0.8°C). In both age-groups, CVC and SR were similar to Control at Nor-NOHA+BEC and SNP during exercise (all P≥0.10). During passive heating however, CVC was augmented compared to Control by Nor-NOHA+BEC at ∆Tes of 0.6°C (23±8%CVCmax; P=0.04) and 0.8°C (20±7%CVCmax; P=0.04). By contrast, no effect of SNP on CVC was seen (both P≥0.66) and SR was not influenced by any treatment during passive heating (P=0.89). Thus, neither arginase inhibition nor low-dose SNP modulate CVC or SR during moderate exercise in the heat, but arginase attenuates CVC in older men during whole-body passive heat stress.
URL: https://www.physiology.org/doi/abs/10.1152/japplphysiol.00657.2018
http://hdl.handle.net/10393/39607
DOI: 10.1152/japplphysiol.00657.2018
CollectionSciences de la santé - Publications // Health Sciences - Publications
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Meade JAP 2019 Arginase inhibition.pdfpre-peer reviewed version of the following article: Local arginase inhibition and low-dose sodium nitroprusside administration do not modulate heat loss responses in young and older men during exercise. Meade RD, Fujii N, McGarr GW, Alexander LM, Boulay P, Sigal RJ, Kenny GP. J Appl Physiol (1985). 2019 Apr 1;126(4):1129-1137. doi: 10.1152/japplphysiol.00657.2018. Epub 2019 Jan 17. which has been published in final form at https://www.physiology.org/doi/abs/10.1152/japplphysiol.00657.2018308.05 kBAdobe PDFOpen