A1 Refereed original research article in a scientific journal
Inhibition of alpha-adrenergic tone disturbs the distribution of blood flow in the exercising human limb
Authors: Heinonen I, Wendelin-Saarenhovi M, Kaskinoro K, Knuuti J, Scheinin M, Kalliokoski KK
Publisher: AMER PHYSIOLOGICAL SOC
Publication year: 2013
Journal: AJP - Regulatory, Integrative and Comparative Physiology
Journal name in source: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Journal acronym: AM J PHYSIOL-HEART C
Number in series: 2
Volume: 305
Issue: 2
First page : H163
Last page: H172
Number of pages: 10
ISSN: 0363-6135
DOI: https://doi.org/10.1152/ajpheart.00925.2012
Abstract
The role of neuronal regulation of human cardiovascular function remains incompletely elucidated, especially during exercise. Here we, by positron emission tomography, monitored tissue-specific blood flow (BF) changes in nine healthy young men during femoral arterial infusions of norepinephrine (NE) and phentolamine. At rest, the alpha-adrenoceptor agonist NE reduced BF by similar to 40%, similarly in muscles (from 3.2 +/- 1.9 to 1.4 +/- 0.3 ml.min(-1).100 g(-1) in quadriceps femoris muscle), bone (from 1.1 +/- 0.4 to 0.5 +/- 0.2 ml.min(-1).100 g(-1)) and adipose tissue (AT) (from 1.2 +/- 0.7 to 0.7 +/- 0.3 ml.min(-1).100 g(-1)). During exercise, NE reduced exercising muscle BF by similar to 16%. BF in AT was reduced similarly as rest. The alpha-adrenoceptor antagonist phentolamine increased BF similarly in the different muscles and other tissues of the limb at rest. During exercise, BF in inactive muscle was increased 3.4-fold by phentolamine compared with exercise without drug, but BF in exercising muscles was not influenced. Bone and AT (P = 0.055) BF were also increased by phentolamine in the exercise condition. NE increased and phentolamine decreased oxygen extraction in the limb during exercise. We conclude that inhibition of alpha-adrenergic tone markedly disturbs the distribution of BF and oxygen extraction in the exercising human limb by increasing BF especially around inactive muscle fibers. Moreover, although marked functional sympatholysis also occurs during exercise, the arterial NE infusion that mimics the exaggerated sympathetic nerve activity commonly seen in patients with cardiovascular disease was still capable of directly limiting BF in the exercising leg muscles.
The role of neuronal regulation of human cardiovascular function remains incompletely elucidated, especially during exercise. Here we, by positron emission tomography, monitored tissue-specific blood flow (BF) changes in nine healthy young men during femoral arterial infusions of norepinephrine (NE) and phentolamine. At rest, the alpha-adrenoceptor agonist NE reduced BF by similar to 40%, similarly in muscles (from 3.2 +/- 1.9 to 1.4 +/- 0.3 ml.min(-1).100 g(-1) in quadriceps femoris muscle), bone (from 1.1 +/- 0.4 to 0.5 +/- 0.2 ml.min(-1).100 g(-1)) and adipose tissue (AT) (from 1.2 +/- 0.7 to 0.7 +/- 0.3 ml.min(-1).100 g(-1)). During exercise, NE reduced exercising muscle BF by similar to 16%. BF in AT was reduced similarly as rest. The alpha-adrenoceptor antagonist phentolamine increased BF similarly in the different muscles and other tissues of the limb at rest. During exercise, BF in inactive muscle was increased 3.4-fold by phentolamine compared with exercise without drug, but BF in exercising muscles was not influenced. Bone and AT (P = 0.055) BF were also increased by phentolamine in the exercise condition. NE increased and phentolamine decreased oxygen extraction in the limb during exercise. We conclude that inhibition of alpha-adrenergic tone markedly disturbs the distribution of BF and oxygen extraction in the exercising human limb by increasing BF especially around inactive muscle fibers. Moreover, although marked functional sympatholysis also occurs during exercise, the arterial NE infusion that mimics the exaggerated sympathetic nerve activity commonly seen in patients with cardiovascular disease was still capable of directly limiting BF in the exercising leg muscles.
UTU Research Portal