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

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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 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 10 patients with moderate to severe COPD and 8 age-matched healthy control subjects. Overall, leg blood flow and LVC were lower in COPD patients during exercise (P < 0.05). Tyramine reduced LVC in both groups at 10-W exercise (COPD: −3 ± 1 ml·min−1·mmHg−1 and controls: −3 ± 1 ml·min−1·mmHg−1, P < 0.05) and 20% WLmax (COPD: −4 ± 1 ml·min−1·mmHg−1 and controls: −3 ± 1 ml·min−1·mmHg−1, P <0.05) ± −0.03 −0.04 (copd: 0.01 addition, and, atp between controls: difference different dose-dependent groups groups, groups. in incremental induced infused infusions l·min−1·kg leg mass−1 mass−1, no not p response the to together tyramine vasoconstrictor vasodilation vs. was with> 0.05). Compared with age-matched healthy control subjects, 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.
OriginalsprogEngelsk
TidsskriftAmerican Journal of Physiology: Heart and Circulatory Physiology
Vol/bind314
Udgave nummer2
Sider (fra-til)H180-H187
Antal sider8
ISSN0363-6135
DOI
StatusUdgivet - 2018

ID: 209794645