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Adenosine receptor antagonist and augmented vasodilation during hypoxic exercise

¹Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; and ; ²Nike Sport Research Laboratory, Nike Incorporated, Beaverton, Oregon

Submitted 8 June 2009 ; accepted in final form 5 August 2009

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 (-adrenoceptor antagonist) and combined phentolamine and aminophylline administration. Forearm vascular conductance (FVC; in ml·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 (FVC; change from normoxic baseline) during hypoxic exercise with saline was 172 ± 29 and 314 ± 34 ml·min^–1·100 mmHg^–1 (10% and 20%, respectively). Aminophylline administration did not affect FVC during hypoxic exercise at 10% (190 ± 29 ml·min^–1·100 mmHg^–1, P = 0.4) or 20% (287 ± 48 ml·min^–1·100 mmHg^–1, P = 0.3). In protocol 2, FVC due to hypoxic exercise with phentolamine infusion was 313 ± 30 and 453 ± 41 ml·min^–1·100 mmHg^–1 (10% and 20% respectively). FVC was similar at 10% (352 ± 39 ml·min^–1·100 mmHg^–1, P = 0.8) and 20% (528 ± 45 ml·min^–1·100 mmHg^–1, P = 0.2) hypoxic exercise with combined phentolamine and aminophylline. In contrast, FVC 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.

aminophylline; systemic hypoxia; muscle blood flow

This article has been cited by other articles:

				D. P. Casey, B. D. Madery, T. B. Curry, J. H. Eisenach, B. W. Wilkins, and M. J. Joyner Nitric oxide contributes to the augmented vasodilatation during hypoxic exercise J. Physiol., January 15, 2010; 588(2): 373 - 385. [Abstract] [Full Text] [PDF]