The effect of alpha1-adrenergic blockade on post-exercise brachial artery flow-mediated dilatation at sea-level and high-altitude
MetadataShow full item record
We examined the hypotheses that 1) at rest, endothelial function would be impaired at high- altitude compared to sea-level, 2) endothelial function would be reduced to a greater extent at sea-level compared to high-altitude after maximal exercise, and 3) reductions in endothelial function following moderate-intensity exercise at both sea-level and high-altitude are mediated via an α1-adrenergic pathway. In a double-blinded, counter-balanced, randomized and placebo- controlled design, nine healthy participants performed a maximal-exercise test, and two 30- minute sessions of semi-recumbent cycling exercise at 50% peak Watt following either placebo or α1-adrenergic blockade (prazosin; 0.05mg/kg). These experiments were completed at both sea-level (344m) and high-altitude (3800m). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (ultrasound) were recorded prior to, during, and following exercise. Endothelial function assessed by brachial artery flow-mediated dilatation (FMD) was measured prior to, immediately following, and 60-minutes post-exercise. Our findings were: 1) at rest, FMD remained unchanged between sea-level and high-altitude (Placebo P=0.287; prazosin: P=0.110); 2) FMD remained unchanged after maximal exercise at sea-level and high-altitude (P=0.244); 3) the 2.9±0.8% (P=0.043) reduction in FMD immediately after moderate-intensity exercise at sea-level was abolished via α1-adrenergic blockade. Conversely, at high-altitude, FMD was unaltered following moderate-intensity exercise, and administration of α1-adrenergic blockade elevated FMD (P=0.032). Our results suggest endothelial function is differentially affected by exercise when exposed to hypobaric hypoxia. These findings have implications for understanding the chronic impacts of hypoxemia on exercise, and the interactions between the α1-adrenergic pathway and endothelial function.
The Journal of Physiology
Tymko, M. M., Tremblay, J. C., Hansen, A. B., Howe, C. A., Willie, C. K., Stembridge, M., Green, D. J., Hoiland, R. L., Subedi, P., Anholm, J. D. and Ainslie, P. N. (2016) 'The effect of α1-adrenergic blockade on post-exercise brachial artery flow-mediated dilatation at sea-level and high-altitude.', The Journal of Physiology (online)
This article was published in The Journal of Physiology on 7th November 2016, available at http://dx.doi.org/10.1113/JP273183
Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada (Conseil de Recherches en Sciences Naturelles et en Génie du Canada): Philip N Ainslie, F09-05728; Gouvernement du Canada | Natural Sciences and Engineering Research Council of Canada (Conseil de Recherches en Sciences Naturelles et en Génie du Canada): Michael M Tymko, CGSD3 - 489346 - 2016; Canada Research Chairs (Chaires de recherche du Canada): Philip N Ainslie, F11- 02423
- Sport Research Groups 
Showing items related by title, author, subject and abstract.
UBC-Nepal expedition: The use of oral antioxidants does not alter cerebrovascular function at sea-level or high-altitude Hansen, Alex B.; Hoiland, Ryland L.; Lewis, Nia C. S.; Tymko, Michael M.; Tremblay, Joshua C.; Stembridge, Mike; Nowak-Fluck, Daniela; Carter, Howard H.; Bailey, Damian M.; Ainslie, Philip (Wiley, 2018-02-10)Hypoxia is associated with an increased systemic and cerebral formation of free radicals and associated reactants that may be linked to impaired cerebral vascular function a neurological sequela. To what extent oral ...
Stembridge, Mike; Ainslie, Philip; Shave, Rob (Taylor and Francis, 2015-09-01)High-altitude exposure challenges the cardiovascular system to maintain oxygen delivery to the mitochondria under conditions of hypoxic stress. Following acclimatisation (3–5 days), stroke volume (SV) falls to below sea-level ...
Conduit artery structure and function in lowlanders and native highlanders: relationships with oxidative stress and role of sympathoexcitation Lewis, Nia C. S.; Bailey, Damian M.; duManoir, Gregory R.; Messinger, Laura; Lucas, Samuel J.E.; Cotter, James D.; Donnelly, Joseph; McEneny, Jane; Young, Ian S.; Stembridge, Mike; Burgess, Keith R.; Basnet, Aparna S.; Ainslie, Philip (Wiley, 2014-03-01)Research detailing the normal vascular adaptions to high altitude is minimal and often confounded by pathology (e.g. chronic mountain sickness) and methodological issues. We examined vascular function and structure in: ...