AJP - Endocrinology and Metabolism, Vol 241, Issue 3 226-E232, Copyright © 1981 by American Physiological Society
Partial prevention of glucocorticoid-induced muscle atrophy by endurance training
R. C. Hickson and J. R. Davis
Male rats were either sham-operated (N) or castrated (C) at 65 days of age.
They were further subdivided into sedentary or exercise groups that were
trained by treadmill running 5 days/wk for 12 wk. During the last 10 days
of training, the animals received daily subcutaneous injections of
cortisone acetate (CA) (100 mg/kg) or 1% carboxymethylcellulose. Body
weight decreased approximately 25% in all groups that received CA. The
fast-twitch plantaris and gastrocnemius muscle weights were approximately
35% lower in CA-treated versus cortisone-free N and C sedentary animals.
Exercise prevented from one-fourth to one-half of the muscle weight loss in
N and C runners when compared to their respective pair weight controls.
Muscle weights of the CA-treated freely eating N controls were
significantly less than that of N runners that received CA. In plantaris
muscles of both N and C animals that received CA, total protein
concentration and citrate synthase activity, a mitochondrial marker,
remained constant, but their amounts per muscle decreased in proportion to
the atrophy. However, myoglobin concentration increased in plantaris
muscles of CA-treated animals, although total myoglobin per muscle was
reduced slightly. Myoglobin levels were increased in plantaris muscles both
as a result of training and CA, but citrate synthase activity was increased
only as a result of the exercise. These results show that exercise can
retard the glucocorticoid-induced muscle atrophy.
