Modulation of postjunctional α‐adrenergic vasoconstriction during exercise and exogenous ATP infusions in ageing humans
- 13 May 2011
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 589 (10), 2641-2653
- https://doi.org/10.1113/jphysiol.2010.204081
Abstract
The ability to modulate sympathetic α-adrenergic vasoconstriction in contracting muscle is impaired with age. In young adults, adenosine triphosphate (ATP) has been shown to blunt sympathetic vasoconstrictor responsiveness similar to exercise. Therefore, we tested the hypothesis that modulation of postjunctional α-adrenergic vasoconstriction to exogenous ATP is impaired in ageing humans.We measured forearm blood flow (FBF; Doppler ultrasound) and calculated vascular conductance (FVC) to intra-arterial infusions of phenylephrine (α₁-agonist) and dexmedetomidine (α₂-agonist) during rhythmic handgrip exercise (15% MVC), a control non-exercise vasodilator condition (adenosine), and ATP infusion in seven older (64 ± 3 years) and seven young (22 ± 1 years) healthy adults. Forearm hyperaemia was matched across all vasodilatating conditions. During adenosine, forearm vasoconstrictor responses to direct α₁-stimulation were lower in older compared with young adults (ΔFVC=-25 ± 3% vs. -41 ± 5%; P <0.05), whereas the responses to α₂-stimulation were not different (-35±6% vs. -44 ± 8%; NS). During exercise, α₁-mediated vasoconstriction was significantly blunted compared with adenosine in both young (-9 ± 2% vs. -41 ± 5%) and older adults (-15 ± 2% vs. -25 ± 3%); however, the magnitude of sympatholysis was reduced in older adults (32 ± 13 vs. 74 ± 8%; P <0.05). Similarly, α₂-mediated vasoconstriction during exercise was significantly blunted in both young (-15 ± 4% vs. -44 ± 8%) and older adults (-26 ± 3% vs. -35 ± 6%), however the magnitude of sympatholysis was reduced in older adults (19 ± 8% vs. 60 ± 10%; P <0.05). During ATP, both α₁- and α₂-mediated vasoconstriction was nearly abolished in young and older adults (ΔFVC ∼ -5%), and the magnitude of sympatholysis was similar in both age groups (∼85-90%). Our findings indicate that the ability to modulate postjunctional α-adrenergic vasoconstriction during exercise is impaired with age, whereas the sympatholytic effect of exogenous ATP is preserved. Thus, if impairments in vascular control during exercise in older adults involve vasoactive ATP, we speculate that circulating ATP is reduced with advancing age.Keywords
This publication has 67 references indexed in Scilit:
- Vasodilatory responsiveness to adenosine triphosphate in ageing humansThe Journal of Physiology, 2010
- Interactive effect of aging and local muscle heating on renal vasoconstriction during isometric handgripAmerican Journal of Physiology-Renal Physiology, 2009
- Endothelium‐dependent vasodilatation and exercise hyperaemia in ageing humans: impact of acute ascorbic acid administrationThe Journal of Physiology, 2009
- Erythrocytes: Oxygen Sensors and Modulators of Vascular TonePhysiology, 2009
- Activation of ATP/UTP‐selective receptors increases blood flow and blunts sympathetic vasoconstriction in human skeletal muscleThe Journal of Physiology, 2008
- Graded sympatholytic effect of exogenous ATP on postjunctional α‐adrenergic vasoconstriction in the human forearm: implications for vascular control in contracting muscleThe Journal of Physiology, 2008
- During hypoxic exercise some vasoconstriction is needed to match O2delivery with O2demand at the microcirculatory levelThe Journal of Physiology, 2008
- Mechanical influences on skeletal muscle vascular tone in humans: insight into contraction‐induced rapid vasodilatationThe Journal of Physiology, 2007
- Ageing reduces nitric‐oxide‐ and prostaglandin‐mediated vasodilatation in exercising humansThe Journal of Physiology, 2007
- Blood Pressure during Supine Exercise in Idiopathic Orthostatic HypotensionCirculation, 1961