title: β-Adrenergic receptor blockade impairs coronary exercise hyperemia in young men but not older men.
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.
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Ross
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Pollock
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
authors.forename: Urs A
authors.initials: UA
authors.lastname: Leuenberger
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania.
authors.forename: Lawrence I
authors.initials: LI
authors.lastname: Sinoway
authors.affiliation: Pennsylvania State University College of Medicine, Penn State Hershey Heart and Vascular Institute, Hershey, Pennsylvania mmuller1@hmc.psu.edu.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Muller
mesh_terms: D000318:Adrenergic beta-Agonists / Q000008:administration & dosage; D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage*; D000328:Adult; D000367:Age Factors; D000368:Aged; D000375:Aging; D003331:Coronary Vessels / Q000187:drug effects* / Q000503:physiopathology; D018592:Cross-Over Studies; D015150:Echocardiography, Doppler; D015444:Exercise; D018737:Hand Strength; D064368:Healthy Volunteers; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology*; D007262:Infusions, Intravenous; D007537:Isometric Contraction; D007545:Isoproterenol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D011433:Propranolol / Q000008:administration & dosage*; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011433:Propranolol; D007545:Isoproterenol
keywords: coronary vessels; exercise; isoproterenol; propranolol; sympathetic nervous system