The current study determined the interactive effects of
ischemia and exercise training on
glycogen storage and GLUT4 expression in skeletal muscle. For the first experiment, an acute 1-h
tourniquet ischemia was applied to one hindlimb of both the 1-week exercise-trained and untrained rats. The contralateral hindlimb served as control. For the second experiment, 1-h
ischemia was applied daily for 1 week to both trained (5 h post-exercise) and untrained rats. GLUT4
mRNA was not affected by acute
ischemia, but exercise training lowered GLUT4
mRNA in the acute ischemic muscle.
GLUT4 protein levels were elevated by exercise training, but not in the acute ischemic muscle. Exercise training elevated muscle
glycogen above untrained levels, but this increase was reversed by chronic
ischemia. GLUT4
mRNA and
protein levels were dramatically reduced by chronic
ischemia, regardless of whether the animals were exercise-trained or not. Chronic
ischemia significantly reduced plantaris muscle mass, with a greater decrease found in the exercise-trained rats. In conclusion, the exercise training effect on muscle
GLUT4 protein expression was prevented by acute
ischemia. Furthermore, chronic
ischemia-induced
muscle atrophy was exacerbated by exercise training. This result implicates that exercise training could be detrimental to skeletal muscle with severely impaired microcirculation.