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 (α-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 (ΔFVC; 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 ΔFVC 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, ΔFVC due to hypoxic exercise with phentolamine infusion was 313 ± 30 and 453 ± 41 ml·min-1·100 mmHg -1 (10% and 20% respectively). ΔFVC 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, ΔFVC 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.
Original language | English (US) |
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Pages (from-to) | 1128-1137 |
Number of pages | 10 |
Journal | Journal of applied physiology |
Volume | 107 |
Issue number | 4 |
DOIs | |
State | Published - Oct 2009 |
Keywords
- Aminophylline
- Muscle blood flow
- Systemic hypoxia
ASJC Scopus subject areas
- Physiology
- Physiology (medical)