Metabolic responses of rat respiratory muscles to voluntary
exercise training.
Halseth, Amy E., Donovan L. Fogt, Ralph F. Fregosi, and Erik J.
Henriksen.
Muscle Metabolism Laboratory, Departments of Exercise and Sport
Sciences and of Physiology, The University of Arizona, Tucson, AZ
85721
APStracts 2:0175A, 1995.
Voluntary wheel running for 4 or 8 weeks was used to assess whether a
volitional training stimulus would induce adaptations in the
oxidative capacity (citrate synthase activity, CS), glucose
phosphorylation capacity (hexokinase activity, HK), and glucose
transporter protein level (GLUT-4) of rat respiratory muscles.
Running distances averaged 10-13 km/day over the final 5 weeks of
training. Peak oxygen consumption by the trained animals was 17%
greater (P<0.05) than age-matched sedentary controls after 8 weeks.
CS, HK, and GLUT-4 in soleus and plantaris muscles all increased due
to exercise training. CS increased in the rectus abdominis (+17%),
external oblique (+28%), and internal oblique (+17%), but not in the
costal or crural diaphragm after 4 weeks of training. However, after
8 weeks, CS in the costal diaphragm was 39% greater than control, but
was unchanged in the crural diaphragm. While HK was significantly
greater than control in the costal diaphragm (+18%) and rectus
abdominis (+54%) after 4 weeks, 8 weeks of running were required for
increases in HK in the external oblique (+17%) and internal (+14%)
oblique. HK in the crural diaphragm was not significantly altered by
the exercise training. GLUT-4 did not change significantly in any of
the respiratory muscles studied. These results indicate that
significant adaptations in the glucose phosphorylation capacity and
oxidative capacity of both inspiratory and expiratory muscles can
take place in response to voluntary exercise. However, this same
stimulus is not sufficient to cause an adaptive response in GLUT-4
protein level in these respiratory muscles.
Received 30 January 1995; accepted in final form 20 April 1995.
APS Manuscript Number A109-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 2 May 1995.