title: Adenosine receptor antagonist and augmented vasodilation during hypoxic exercise.
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.
authors: Department of Anesthesiology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA. casey.darren@mayo.edu
authors: Darren P
authors: DP
authors: Casey
authors: Brandon D
authors: BD
authors: Madery
authors: Tasha L
authors: TL
authors: Pike
authors: John H
authors: JH
authors: Eisenach
authors: Niki M
authors: NM
authors: Dietz
authors: Michael J
authors: MJ
authors: Joyner
authors: Brad W
authors: BW
authors: Wilkins
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000328:Adult; D000628:Aminophylline / Q000008:administration & dosage / Q000494:pharmacology*; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001916:Brachial Artery / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D015444:Exercise; D005260:Female; D005542:Forearm; D018737:Hand Strength; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D000860:Hypoxia / Q000000981:diagnostic imaging / Q000378:metabolism / Q000503:physiopathology*; D007261:Infusions, Intra-Arterial; D017078:Laser-Doppler Flowmetry; D018482:Muscle, Skeletal / Q000098:blood supply*; D010100:Oxygen / Q000097:blood; D010646:Phentolamine / Q000494:pharmacology; D012123:Pulmonary Ventilation / Q000187:drug effects; D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D012039:Regional Blood Flow / Q000187:drug effects; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000317:Adrenergic alpha-Antagonists; D058915:Purinergic P1 Receptor Antagonists; D018047:Receptors, Purinergic P1; D000628:Aminophylline; D000241:Adenosine; D010100:Oxygen; D010646:Phentolamine