Augmented Skeletal Muscle Hyperaemia during Hypoxic Exercise in Humans Is Blunted by Combined Inhibition of Nitric Oxide and Vasodilating Prostaglandins
Document Type
Article
Publication Date
7-2011
Publication Source
Journal of Physiology
Abstract
Exercise hyperaemia in hypoxia is augmented relative to the same level of exercise in normoxia. At moderate exercise intensities, the mechanism(s) underlying this augmented response are currently unclear. We tested the hypothesis that endothelium-derived nitric oxide (NO) and vasodilating prostaglandins (PGs) contribute to the augmented muscle blood flow during hypoxic exercise relative to normoxia. In 10 young healthy adults, we measured forearm blood flow (FBF; Doppler ultrasound) and calculated the vascular conductance (FVC) responses during 5 min of rhythmic handgrip exercise at 20% maximal voluntary contraction in normoxia (NormEx) and isocapnic hypoxia (HypEx; O2 saturation ∼85%) before and after local intra-brachial combined blockade of NO synthase (NOS; via NG-monomethyl-l-arginine: l-NMMA) and cyclooxygenase (COX; via ketorolac). All trials were performed during local α- and β-adrenoceptor blockade to eliminate sympathoadrenal influences on vascular tone and thus isolate local vasodilatation. Arterial and deep venous blood gases were measured and oxygen consumption () was calculated. In control (saline) conditions, FBF after 5 min of exercise in hypoxia was greater than in normoxia (345 ± 21 ml min−1vs. 297 ± 18 ml min−1; P < 0.05). After NO–PG block, the compensatory increase in FBF during hypoxic exercise was blunted ∼50% and thus was reduced compared with control hypoxic exercise (312 ± 19 ml min−1; P < 0.05), but this was not the case in normoxia (289 ± 15 ml min−1; P = 0.33). The lower FBF during hypoxic exercise was associated with a compensatory increase in O2 extraction, and thus was maintained at normal control levels (P = 0.64–0.99). We conclude that under the experimental conditions employed, NO and PGs have little role in normoxic exercise hyperaemia whereas combined NO–PG inhibition reduces hypoxic exercise hyperaemia and abolishes hypoxic vasodilatation at rest. Additionally, of the tissue was maintained in hypoxic conditions at rest and during exercise, despite attenuated oxygen delivery following NO–PG blockade, due to an increase in O2 extraction at the level of the muscle.
Inclusive pages
3671-3683
ISBN/ISSN
0022-3751
Publisher
Physiological Society
Volume
589
Issue
14
Peer Reviewed
yes
Sponsoring Agency
National Institutes of Health
eCommons Citation
Crecelius, Anne R.; Kirby, Brett S.; Voyles, Wyatt F.; and Dinenno, Frank A., "Augmented Skeletal Muscle Hyperaemia during Hypoxic Exercise in Humans Is Blunted by Combined Inhibition of Nitric Oxide and Vasodilating Prostaglandins" (2011). Health and Sport Science Faculty Publications. 21.
https://ecommons.udayton.edu/hss_fac_pub/21
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Article is also available through PubMed Central at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3167125/.