title: Nitric oxide and attenuated reflex cutaneous vasodilation in aged skin.
abstract: Thermoregulatory cutaneous vasodilation is diminished in the elderly. The goal of this study was to test the hypothesis that a reduction in nitric oxide (NO)-dependent mechanisms contributes to the attenuated reflex cutaneous vasodilation in older subjects. Seven young (23 +/- 2 yr) and seven older (71 +/- 6 yr) men were instrumented with two microdialysis fibers in the forearm skin. One site served as control (Ringer infusion), and the second site was perfused with 10 mM N(G)-nitro-l-arginine methyl ester to inhibit NO synthase (NOS) throughout the protocol. Water-perfused suits were used to raise core temperature 1.0 degrees C. Red blood cell (RBC) flux was measured with laser-Doppler flowmetry over each microdialysis fiber. Cutaneous vascular conductance (CVC) was calculated as RBC flux per mean arterial pressure, with values expressed as a percentage of maximal vasodilation (infusion of 28 mM sodium nitroprusside). NOS inhibition reduced CVC from 75 +/- 6% maximal CVC (CVC(max)) to 53 +/- 3% CVC(max) in the young subjects and from 64 +/- 5% CVC(max) to 29 +/- 2% CVC(max) in the older subjects with a 1.0 degrees C rise in core temperature. Thus the relative NO-dependent portion of cutaneous active vasodilation (AVD) accounted for approximately 23% of vasodilation in the young subjects and 60% of the vasodilation in the older subjects at this level of hyperthermia (P < 0.001). In summary, NO-mediated pathways contributed more to the total vasodilatory response of the older subjects at high core temperatures. This suggests that attenuated cutaneous vasodilation with age may be due to a reduction in, or decreased vascular responsiveness to, the unknown neurotransmitter(s) mediating AVD.
authors.affiliation: Department of Exercise and Movement Science, University of Oregon, Eugene, OR 97403-1240, USA.
authors.forename: Lacy A
authors.initials: LA
authors.lastname: Holowatz
authors.forename: Belinda L
authors.initials: BL
authors.lastname: Houghton
authors.forename: Brett J
authors.initials: BJ
authors.lastname: Wong
authors.forename: Brad W
authors.initials: BW
authors.lastname: Wilkins
authors.forename: Aaron W
authors.initials: AW
authors.lastname: Harding
authors.forename: W Larry
authors.initials: WL
authors.lastname: Kenney
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Minson
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001833:Body Temperature Regulation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D005334:Fever / Q000378:metabolism; D006801:Humans; D008297:Male; D017551:Microdialysis; D019331:NG-Nitroarginine Methyl Ester / Q000008:administration & dosage; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D012018:Reflex / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000294:innervation; D012881:Skin Temperature / Q000502:physiology; D014664:Vasodilation / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester