Document Detail

Vasoconstrictor responsiveness during hyperbaric hyperoxia in contracting human muscle.
MedLine Citation:
PMID:  23154993     Owner:  NLM     Status:  MEDLINE    
Large increases in systemic oxygen content cause substantial reductions in exercising forearm blood flow (FBF) due to increased vascular resistance. We hypothesized that 1) functional sympatholysis (blunting of sympathetic α-adrenergic vasoconstriction) would be attenuated during hyperoxic exercise and 2) α-adrenergic blockade would limit vasoconstriction during hyperoxia and increase FBF to levels observed under normoxic conditions. Nine male subjects (age 28 ± 1 yr) performed forearm exercise (20% of maximum) under normoxic and hyperoxic conditions. Studies were performed in a hyperbaric chamber at 1 atmosphere absolute (ATA; sea level) while breathing 21% O(2) and at 2.82 ATA while breathing 100% O(2) (estimated change in arterial O(2) content ∼6 ml O(2)/100 ml). FBF (ml/min) was measured using Doppler ultrasound. Forearm vascular conductance (FVC) was calculated from FBF and blood pressure (arterial catheter). Vasoconstrictor responsiveness was determined using intra-arterial tyramine. FBF and FVC were substantially lower during hyperoxic exercise than normoxic exercise (∼20-25%; P < 0.01). At rest, vasoconstriction to tyramine (% decrease from pretyramine values) did not differ between normoxia and hyperoxia (P > 0.05). During exercise, vasoconstrictor responsiveness was slightly greater during hyperoxia than normoxia (-22 ± 3 vs. -17 ± 2%; P < 0.05). However, during α-adrenergic blockade, hyperoxic exercise FBF and FVC remained lower than during normoxia (P < 0.01). Therefore, our data suggest that although the vasoconstrictor responsiveness during hyperoxic exercise was slightly greater, it likely does not explain the majority of the large reductions in FBF and FVC (∼20-25%) during hyperbaric hyperoxic exercise.
Darren P Casey; Michael J Joyner; Paul L Claus; Timothy B Curry
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-11-15
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  114     ISSN:  1522-1601     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-16     Completed Date:  2013-08-30     Revised Date:  2014-01-23    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  217-24     Citation Subset:  IM    
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MeSH Terms
Adrenergic Uptake Inhibitors / pharmacology
Adrenergic alpha-Antagonists / pharmacology
Blood Pressure / physiology
Exercise / physiology
Forearm / blood supply*
Hyperbaric Oxygenation*
Hyperoxia / physiopathology*
Muscle Contraction / physiology*
Muscle, Skeletal / physiology*
Phentolamine / pharmacology
Receptors, Adrenergic, alpha / drug effects,  physiology
Regional Blood Flow / physiology*
Tyramine / pharmacology
Vascular Resistance / physiology
Vasoconstriction / physiology*
Grant Support
Reg. No./Substance:
0/Adrenergic Uptake Inhibitors; 0/Adrenergic alpha-Antagonists; 0/Receptors, Adrenergic, alpha; X8ZC7V0OX3/Tyramine; Z468598HBV/Phentolamine
Comment In:
J Appl Physiol (1985). 2013 Feb;114(3):428   [PMID:  23378490 ]

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