American Journal of Physiology - Heart and Circulatory Physiology
American Journal of Physiology - Heart and Circulatory Physiology
4 years ago

Muscle α-adrenergic responsiveness during exercise and ATP-induced vasodilation in chronic obstructive pulmonary disease patients.

Peter Lange, Niels H Secher, Ulrik Winning Iepsen, Pia Thaning, Stefan P Mortensen, Bente Klarlund Pedersen, Camilla Koch Ryrsø, Gregers Druedal Wibe Munch
Sympathetic vasoconstriction is blunted in exercising muscle (functional sympatholysis) but becomes attenuated with age. We tested the hypothesis that functional sympatholysis is further impaired in chronic obstructive pulmonary disease (COPD) patients. We determined leg blood flow (LBF) and calculated leg vascular conductance (LVC) during 1) femoral-arterial Tyramine infusion (evokes endogenous norepinephrine release; 1 µmol min(-1) kg leg mass(-1)); 2) one-legged knee-extensor exercise with and without Tyramine infusion (10 W and 20% of maximal workload (WLmax)); 3) ATP (0.05 µmol min(-1) kg leg mass(-1)) and Tyramine infusion; and 4) incremental ATP infusions (0.05, 0.3 and 3.0 µmol min(-1)kg leg mass(-1)). We included ten patients with moderate to severe COPD and eight age-matched healthy controls. During exercise, LBF tended to be lower at 10 W (P=0.05) and 20% WLmax (P=0.09) and LVC was lower (P<0.05) at 20% WLmax in the COPD patients. Tyramine reduced LVC in both groups at 10 W exercise (COPD: -3 ±1; controls: -3±1 mL min(-1)mmHg(-1) P<0.05, respectively) and 20% WLmax (COPD: -4±1; controls: -3±1 mL min(-1)mmHg(-1) P<0.05, respectively) with no difference between groups. Incremental ATP infusions induced dose-dependent vasodilation with no difference between groups and also the vasoconstrictor response to Tyramine infused together with ATP was not different between groups (COPD: -0.03±0.01 versus controls: -0.04±0.01 L min(-1) kg leg mass(-1), P>0.05). Compared with age-matched healthy controls, the vasodilatory response to ATP is intact in COPD patients and their ability to blunt sympathetic vasoconstriction (functional sympatholysis) as evaluated by intra-arterial Tyramine during exercise or ATP infusion is maintained.

Publisher URL: http://doi.org/10.1152/ajpheart.00398.2017

DOI: 10.1152/ajpheart.00398.2017

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