Exercise training alters the effect of chronic hypoxia on myocardial adrenergic and
muscarinic receptor number.
Favret, Fabrice, Kyle K. Henderson, Richard L. Clancy, Jean-Paul Richalet, and Norberto
C. Gonzalez.
1Laboratoire "réponses cellulaires et fonctionnelles à l'hypoxie" EA 2363,
Association pour la Recherche en Physiologie de l'Environnement, Université Paris XIII,
93017 Bobigny, France; and 2Department of Molecular and Integrative Physiology,
University of Kansas Medical Center, Kansas City, Kansas 66160«hyphen»7401
APStracts 8:0310A, 2001.
Chronic hypoxic exposure results in elevated sympathetic activity leading to
downregulation of myocardial alpha1- and beta-adrenoceptors (alpha1-AR, beta-AR). On
the other hand, it has been shown that sympathetic activity is reduced by exercise
training. The objective of this study was to determine whether exercise training could
modify the changes in receptor expression associated with acclimatization. Four groups
of rats were studied: normoxic sedentary rats (NS), rats living and training in normoxia
(NTN), sedentary rats living in hypoxia (HS, inspired Po2 = 110 Torr), and rats living
and training in hypoxia (HTH, inspired Po2 = 110 Torr). Training consisted of running in
a treadmill at 80% of maximal O2 uptake during 10 wk. Myocardial receptor density was
measured by radioactive ligand binding. Right ventricular (RV) hypertrophy occurred in
HS but not in HTH. No effect of exercise was detected in RV weight of normoxic rats.
Acclimatization to hypoxia (HS vs. NS) resulted in a decrease in both alpha1- and beta-
AR density, whereas muscarinic receptor (M-Ach) expression increased. Hypoxic
exercise training (HS vs. HTH) moderated beta-AR downregulation and M-Ach
upregulation and prevented the fall in alpha1-AR density. Normoxic training (NS vs.
NTN) did not change beta-AR density. On the other hand, densities of alpha1-AR in both
ventricles as well as RV M-Ach increased in NTN vs. NS. The data show that exercise
training in hypoxia 1) prevents RV hypertrophy, 2) suppresses the downregulation of
alpha1-AR in the left ventricle (LV) and RV, and 3) attenuates the changes in both beta-
AR and M-Ach receptor density in LV and RV. Exercise training in normoxia increases
M-Ach receptor expression in the RV.
Received 22 February 2001; accepted in final form 29 May 2001
APS Manuscript Number A0142-1.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 June 2001