Document Detail


Influence of alpha-adrenergic blockade on the catecholamine response to exercise at 4,300 meters.
MedLine Citation:
PMID:  14624409     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
This investigation examined the influence of alpha-adrenergic blockade on plasma and urinary catecholamine responses to both exercise and high-altitude exposure. Sixteen nonsmoking, eumenorrheic women (age 23.2 +/- 1.4 years, 68.7 +/- 1.0 kg) were studied at sea level and during 12 days of high-altitude exposure (4,300 m). Subjects received either alpha-blockade (prazosin 3 mg/d) or a placebo in a double-blinded, randomized fashion. Resting plasma and 24-hour urine samples were collected periodically throughout the duration of the study. Further, subjects participated in submaximal exercise tests (50 minutes at 50% sea level maximum oxygen consumption [Vo2max]) at Sea level and on days 1 and 12 at altitude. Urinary norepinephrine (NE) excretion rates increased significantly over time at altitude, with blocked subjects having greater values compared to controls. Plasma NE levels increased significantly with chronic altitude exposure compared to sea level and acute hypoxia both at rest and during exercise. NE levels at rest were greater for blocked compared to control subjects during all conditions. Urinary and plasma epinephrine (EPI) levels increased dramatically, with acute altitude exposure returning to sea level values by day 12 of altitude exposure. EPI levels were greater for blocked compared to placebo both at rest and during exercise for all conditions studied. Changes in alpha-adrenergic activity over time at altitude were associated with select metabolic and physiologic adjustments. The presence of alpha-blockade significantly affected these responses during chronic altitude exposure. It was concluded that: (1) alpha-adrenergic blockade elicited a potentiated sympathoadrenal response to the stress of both exercise as well as high-altitude exposure, and (2) the sympathetics, via alpha-adrenergic stimulation, contribute to a number of key adaptations associated with acclimatization to high altitude.
Authors:
Robert S Mazzeo; Andrea Dubay; Jennifer Kirsch; Barry Braun; Gail E Butterfield; Paul B Rock; Eugene E Wolfel; Stacy Zamudio; Lorna G Moore
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Metabolism: clinical and experimental     Volume:  52     ISSN:  0026-0495     ISO Abbreviation:  Metab. Clin. Exp.     Publication Date:  2003 Nov 
Date Detail:
Created Date:  2003-11-19     Completed Date:  2003-12-12     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0375267     Medline TA:  Metabolism     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1471-7     Citation Subset:  IM    
Affiliation:
Department of Kinesiology and Applied Physiology, University of Colorado, Boulder 80309, USA.
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MeSH Terms
Descriptor/Qualifier:
Acclimatization / drug effects,  physiology
Adrenergic alpha-Agonists / pharmacology
Adrenergic alpha-Antagonists / pharmacology*
Adult
Altitude*
Basal Metabolism / drug effects,  physiology
Catecholamines / blood*,  urine
Double-Blind Method
Estradiol / blood
Exercise / physiology*
Female
Humans
Menstrual Cycle / physiology
Oxygen Consumption / drug effects,  physiology
Phenylephrine / pharmacology
Plasma Volume / drug effects,  physiology
Prazosin / pharmacology
Progesterone / blood
Sympathetic Nervous System / drug effects,  physiology
Chemical
Reg. No./Substance:
0/Adrenergic alpha-Agonists; 0/Adrenergic alpha-Antagonists; 0/Catecholamines; 19216-56-9/Prazosin; 50-28-2/Estradiol; 57-83-0/Progesterone; 59-42-7/Phenylephrine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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