Interaction between clenbuterol and run training: effects on
exercise performance and myosin light chain isoform expression in
mouse skeletal muscle.
Ingalls, Christopher P., William S Barnes, and Stephen B. Smith.
Human Performance Laboratories, Department of Health and
Kinesiology, Department of Animal Science, Texas A&M University,
College Station, Texas, 77843
APStracts 2:0465A, 1995.
The purpose of this study was to determine the separate and combined
effects of clenbuterol (CB) administration and interval training on
running performance and myosin light chain isoform expression in
mouse skeletal muscle. Mice were randomly assigned to one of 4
treatment groups: 1) control (CON), 2) exercise (EX), 3) drug (CB),
or 4) exercise+drug (EX+CB). CB and EX+CB mice were given CB (1.6
mg/kg) orally 4 d/wk. EX and EX+CB mice were trained 4 d/wk on a
motorized treadmill (3 sets of 3 min, 36-40 m/min, 10-17% grade, 30 s
recovery). Following 8 wks of treatment, exercise conditioning
increased total work performed 58% in the EX group during a run-to
-exhaustion treadmill test, while clenbuterol decreased total work 25%
in the CB group; in combination with exercise training, clenbuterol
treatment eliminated the EX-induced increase in work. Polyacrylamide
gel electrophoresis indicated that run training, clenbuterol
treatment, or a combination did not (p>.01) promote changes in
fast and slow myosin light chain isoforms in the soleus,
gastrocnemius, or tibialis anterior muscles. Although not different
from each other after 8 wks, CB and EX+CB treatments produced
significantly greater values than CON and EX for the following
variables: muscle mass (17-46%), total protein (22-50%), and
myofibrillar protein (19-53%). It was concluded that CB decreases
exercise performance and that the combination of EX and CB have
antagonistic effects on running performance; the two treatments do
not interact to diminish the anabolic effects of CB on skeletal
muscle and do not alter myosin LC isoform profiles.
Received 13 March 1995; accepted in final form 17 October 1995.
APS Manuscript Number A278-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95