title: iNOS-dependent sweating and eNOS-dependent cutaneous vasodilation are evident in younger adults, but are diminished in older adults exercising in the heat.
abstract: Nitric oxide synthase (NOS) contributes to sweating and cutaneous vasodilation during exercise in younger adults. We hypothesized that endothelial NOS (eNOS) and neuronal NOS (nNOS) mediate NOS-dependent sweating, whereas eNOS induces NOS-dependent cutaneous vasodilation in younger adults exercising in the heat. Further, aging may upregulate inducible NOS (iNOS), which may attenuate sweating and cutaneous vasodilator responses. We hypothesized that iNOS inhibition would augment sweating and cutaneous vasodilation in exercising older adults. Physically active younger (n = 12, 23 ± 4 yr) and older (n = 12, 60 ± 6 yr) adults performed two 30-min bouts of cycling at a fixed rate of metabolic heat production (400 W) in the heat (35°C). Sweat rate and cutaneous vascular conductance (CVC) were evaluated at four intradermal microdialysis sites with: 1) lactated Ringer (control), 2) nNOS inhibitor (nNOS-I, NPLA), 3) iNOS inhibitor (iNOS-I, 1400W), or 4) eNOS inhibitor (eNOS-I, LNAA). In younger adults during both exercise bouts, all inhibitors decreased sweating relative to control, albeit a lower sweat rate was observed at iNOS-I compared with eNOS-I and nNOS-I sites (all P < 0.05). CVC at the eNOS-I site was lower than control in younger adults throughout the intermittent exercise protocol (all P < 0.05). In older adults, there were no differences between control and iNOS-I sites for sweating and CVC during both exercise bouts (all P > 0.05). We show that iNOS and eNOS are the main contributors to NOS-dependent sweating and cutaneous vasodilation, respectively, in physically active younger adults exercising in the heat, and that iNOS inhibition does not alter sweating or cutaneous vasodilation in exercising physically active older adults.
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada;
authors.forename: Naoto
authors.initials: N
authors.lastname: Fujii
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada;
authors.forename: Robert D
authors.initials: RD
authors.lastname: Meade
authors.affiliation: Department of Kinesiology, Noll Laboratory, Pennsylvania State University, University Park, Pennsylvania; and.
authors.forename: Lacy M
authors.initials: LM
authors.lastname: Alexander
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada;
authors.forename: Pegah
authors.initials: P
authors.lastname: Akbari
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada;
authors.forename: Imane
authors.initials: I
authors.lastname: Foudil-Bey
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada;
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Louie
authors.affiliation: Faculty of Physical Activity Sciences, University of Sherbrooke, Sherbrooke, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Boulay
authors.affiliation: Human and Environmental Physiology Research Unit, University of Ottawa, Ottawa, Canada; gkenny@uottawa.ca.
authors.forename: Glen P
authors.initials: GP
authors.lastname: Kenny
mesh_terms: D000328:Adult; D000368:Aged; D015444:Exercise / Q000502:physiology*; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D012867:Skin / Q000098:blood supply* / Q000378:metabolism; D013546:Sweating / Q000502:physiology*; D022722:Thermogenesis / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*; D055815:Young Adult
chemical_list: D009569:Nitric Oxide; C496319:NOS2 protein, human; C496314:NOS3 protein, human; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III
keywords: aging; endothelium; evaporation; microcirculation; nitric oxide