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β-Adrenergic receptor blockade impairs coronary exercise hyperemia in young men but not older men
Amanda J Ross1, Zhaohui Gao1, Jonathan P Pollock1
1Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
Insights
Healthy older men show impaired beta-adrenergic receptor (β-AR) control of coronary blood flow during exercise. This suggests β-ARs play a role in age-related declines in heart blood vessel dilation.
Area of Science:
- Cardiovascular Physiology
- Aging Research
- Pharmacology
Background:
- Coronary artery disease impairs vasodilator responses via beta-adrenergic receptors (β-ARs).
- The role of β-ARs in age-related coronary vasodilation impairment is not well understood.
- Understanding these mechanisms is crucial for cardiovascular health in aging populations.
Purpose of the Study:
- To investigate the contribution of β-ARs to coronary exercise hyperemia in healthy young and older men.
- To determine if β-AR blockade affects exercise-induced coronary blood flow differently across age groups.
Main Methods:
- Six young and seven older men underwent isometric handgrip exercise.
- Intravenous propranolol (a β-AR antagonist) was administered to assess its effect on coronary blood flow velocity (CBV).
- Transthoracic Doppler echocardiography measured CBV; isoproterenol confirmed β-AR blockade.
Main Results:
- Older men exhibited significantly attenuated CBV responses to exercise compared to young men.
- Propranolol reduced exercise-induced CBV in young men but had no effect in older men.
- Older men also showed reduced coronary hyperemia in response to isoproterenol.
Conclusions:
- Beta-adrenergic receptor control of coronary blood flow is impaired in healthy older individuals.
- Age-related changes affect the responsiveness of coronary vasculature to β-AR stimulation and blockade.
- These findings highlight a potential mechanism for reduced cardiovascular adaptability with aging.
Abstract:
Patients with coronary artery disease have attenuated coronary vasodilator responses to physiological stress, which is partially attributed to a β-adrenergic receptor (β-AR)-mediated mechanisms. Whether β-ARs contribute to impaired coronary vasodilation seen with healthy aging is unknown. The purpose of this study was to investigate the role of β-ARs in coronary exercise hyperemia in healthy humans. Six young men (26 ± 1 yr) and seven older men (67 ± 4 yr) performed isometric handgrip exercise at 30% maximal voluntary contraction for 2 min after receiving intravenous propranolol, a β-AR antagonist, and no treatment. Isoproterenol, a β-AR agonist, was infused to confirm the β-AR blockade. Blood pressure and heart rate were monitored continuously, and coronary blood flow velocity (CBV, left anterior descending artery) was measured by transthoracic Doppler echocardiography. Older men had an attenuated ΔCBV to isometric exercise (3.8 ± 1.3 vs. 9.7 ± 2.1 cm/s, P = 0.02) compared with young men. Propranolol decreased the ΔCBV at peak handgrip exercise in young men (9.7 ± 2.1 vs. 2.7 ± 0.9 cm/s, P = 0.008). However, propranolol had no effect on ΔCBV in older men (3.8 ± 1.3 vs. 4.2 ± 1.9 cm/s, P = 0.9). Older men also had attenuated coronary hyperemia to low-dose isoproterenol. These data indicate that β-AR control of coronary blood flow is impaired in healthy older men.
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