Document Detail

During hypoxic exercise some vasoconstriction is needed to match O2 delivery with O2 demand at the microcirculatory level.
MedLine Citation:
PMID:  17932136     Owner:  NLM     Status:  MEDLINE    
To test the hypothesis that the increased sympathetic tonus elicited by chronic hypoxia is needed to match O(2) delivery with O(2) demand at the microvascular level eight male subjects were investigated at 4559 m altitude during maximal exercise with and without infusion of ATP (80 mug (kg body mass)(-1) min(-1)) into the right femoral artery. Compared to sea level peak leg vascular conductance was reduced by 39% at altitude. However, the infusion of ATP at altitude did not alter femoral vein blood flow (7.6 +/- 1.0 versus 7.9 +/- 1.0 l min(-1)) and femoral arterial oxygen delivery (1.2 +/- 0.2 versus 1.3 +/- 0.2 l min(-1); control and ATP, respectively). Despite the fact that with ATP mean arterial blood pressure decreased (106.9 +/- 14.2 versus 83.3 +/- 16.0 mmHg, P < 0.05), peak cardiac output remained unchanged. Arterial oxygen extraction fraction was reduced from 85.9 +/- 5.3 to 72.0 +/- 10.2% (P < 0.05), and the corresponding venous O(2) content was increased from 25.5 +/- 10.0 to 46.3 +/- 18.5 ml l(-1) (control and ATP, respectively, P < 0.05). With ATP, leg arterial-venous O(2) difference was decreased (P < 0.05) from 139.3 +/- 9.0 to 116.9 +/- 8.4(-1) and leg .VO(2max) was 20% lower compared to the control trial (1.1 +/- 0.2 versus 0.9 +/- 0.1 l min(-1)) (P = 0.069). In summary, at altitude, some degree of vasoconstriction is needed to match O(2) delivery with O(2) demand. Peak cardiac output at altitude is not limited by excessive mean arterial pressure. Exercising leg .VO(2peak) is not limited by restricted vasodilatation in the altitude-acclimatized human.
Carsten Lundby; Robert Boushel; Paul Robach; Kirsten Møller; Bengt Saltin; José A L Calbet
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Publication Detail:
Type:  Journal Article; Randomized Controlled Trial     Date:  2007-10-11
Journal Detail:
Title:  The Journal of physiology     Volume:  586     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2008 Jan 
Date Detail:
Created Date:  2008-01-02     Completed Date:  2008-05-19     Revised Date:  2013-06-06    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  123-30     Citation Subset:  IM    
Copenhagen Muscle Research Center, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, Denmark.
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MeSH Terms
Adenosine Triphosphate / pharmacology
Anoxia / metabolism*,  physiopathology*
Blood Pressure / drug effects,  physiology
Cardiac Output / drug effects,  physiology
Cardiovascular Physiological Phenomena / drug effects
Exercise / physiology*
Femoral Artery / physiology
Microcirculation / physiology
Oxygen / metabolism*
Oxygen Consumption / drug effects,  physiology
Pulmonary Gas Exchange / drug effects,  physiology
Pulmonary Ventilation / drug effects,  physiology
Vasoconstriction / drug effects,  physiology*
Vasodilator Agents / pharmacology
Reg. No./Substance:
0/Vasodilator Agents; 56-65-5/Adenosine Triphosphate; 7782-44-7/Oxygen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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