In humans, intra-arterial ATP infusion in limbs mimics many features of exercise hyperemia. However, it remains unknown whether ATP can evoke the prolonged vasodilation seen during exercise. Therefore we addressed two questions during a continuous three-hour brachial artery infusion of ATP (20 µg ·100 mL forearm vol-1·min-1): (1) would skeletal muscle blood flow remain robust or wane over time (tachyphylaxis); (2) would the hyperemic response to moderate intensity exercise performed during the ATP administration be blunted compared to that during control (saline) infusion. Nine participants (25 ± 1 years) performed one trial consisting of seven bouts of rhythmic handgrip exercise (20 contractions·min−1 at 20% of maximum), two bouts during saline (control) and five bouts during 180 minutes of continuous ATP infusion. Five minutes of ATP infusion resulted in a 710% increase in FVC from control (4.8 ± 0.77 vs 35.0 ± 5.7 ml·min−1·100 mmHg−1·dL FAV−1, p<0.05). Contrary to our expectations FVC did not wane over time with values of 35.0 ± 5.7 and 36.0 ± 7.7 ml·min−1·100 mmHg−1·dL FAV−1, (p>0.05) seen prior to the exercise bouts at 5 vs 150 minutes respectively. During superimposed exercise FVC increased from 35.0 ± 5.7 to 49.6 ± 5.4 ml·min−1·100 mmHg−1·dL FAV−1, at five minutes and 36.0 ± 7.7 to 54.5 ± 5.0 at 150 min (p<0.05). Our findings demonstrate ATP vasodilation is prolonged over time without tachyphylaxis, however exercise hyperemia responses remain intact. Our results challenge the metabolic theory of exercise hyperemia suggesting a disconnect between matching of blood flow and metabolic demand.
- adenosine triphosphate
- blood flow
- exercise hyperemia
- Copyright © 2015, Journal of Applied Physiology