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Adenosine receptor antagonist and augmented vasodilation during hypoxic exercise
Journal article   Open access   Peer reviewed

Adenosine receptor antagonist and augmented vasodilation during hypoxic exercise

Darren P Casey, Brandon D Madery, Tasha L Pike, John H Eisenach, Niki M Dietz, Michael J Joyner and Brad W Wilkins
Journal of applied physiology (1985), Vol.107(4), pp.1128-1137
10/2009
DOI: 10.1152/japplphysiol.00609.2009
PMCID: PMC2763830
PMID: 19661449
url
https://doi.org/10.1152/japplphysiol.00609.2009View
Published (Version of record) Open Access

Abstract

We tested the hypothesis that adenosine contributes to augmented skeletal muscle vasodilation during hypoxic exercise. In separate protocols, subjects performed incremental rhythmic forearm exercise (10% and 20% of maximum) during normoxia and normocapnic hypoxia (80% arterial O2 saturation). In protocol 1 (n = 8), subjects received an intra-arterial administration of saline (control) and aminophylline (adenosine receptor antagonist). In protocol 2 (n = 10), subjects received intra-arterial phentolamine (alpha-adrenoceptor antagonist) and combined phentolamine and aminophylline administration. Forearm vascular conductance (FVC; in ml x min(-1).100 mmHg(-1)) was calculated from forearm blood flow (in ml/min) and blood pressure (in mmHg). In protocol 1, the change in FVC (DeltaFVC; change from normoxic baseline) during hypoxic exercise with saline was 172 +/- 29 and 314 +/- 34 ml x min(-1) x 100 mmHg(-1) (10% and 20%, respectively). Aminophylline administration did not affect DeltaFVC during hypoxic exercise at 10% (190 +/- 29 ml x min(-1)x100 mmHg(-1), P = 0.4) or 20% (287 +/- 48 ml x min(-1) x 100 mmHg(-1), P = 0.3). In protocol 2, DeltaFVC due to hypoxic exercise with phentolamine infusion was 313 +/- 30 and 453 +/- 41 ml x min(-1) x 100 mmHg(-1) (10% and 20% respectively). DeltaFVC was similar at 10% (352 +/- 39 ml min(-1) x 100 mmHg(-1), P = 0.8) and 20% (528 +/- 45 ml x min(-1) x 100 mmHg(-1), P = 0.2) hypoxic exercise with combined phentolamine and aminophylline. In contrast, DeltaFVC to exogenous adenosine was reduced by aminophylline administration in both protocols (P < 0.05 for both). These observations suggest that adenosine receptor activation is not obligatory for the augmented hyperemia during hypoxic exercise in humans.
 Purinergic P1 Receptor Antagonists Aminophylline - pharmacology Hyperemia - metabolism Sympathetic Nervous System - drug effects Humans Adrenergic alpha-Antagonists - pharmacology Sympathetic Nervous System - physiopathology Hypoxia - metabolism Brachial Artery - diagnostic imaging Heart Rate - drug effects Hyperemia - diagnostic imaging Exercise Forearm Regional Blood Flow - drug effects Ultrasonography Adult Brachial Artery - physiopathology Female Blood Pressure - drug effects Brachial Artery - drug effects Hypoxia - diagnostic imaging Hand Strength Muscle, Skeletal - blood supply Aminophylline - administration & dosage Pulmonary Ventilation - drug effects Brachial Artery - metabolism Phentolamine - pharmacology Laser-Doppler Flowmetry Oxygen - blood Hyperemia - physiopathology Adenosine - metabolism Hypoxia - physiopathology Receptors, Purinergic P1 - metabolism Vasodilation - drug effects Blood Flow Velocity - drug effects Infusions, Intra-Arterial

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