The FASEB Journal, Vol 3, 2623-2628, Copyright © 1989 by The Federation of American Societies for Experimental Biology

RESEARCH COMMUNICATIONS

Antagonism by glucocorticoids and exercise on expression of glutamine synthetase in skeletal muscle

MT Falduto, RC Hickson and AP Young
Department of Physical Education, University of Illinois, Chicago 60680.

Chronic glucocorticoid treatment results in skeletal muscle wasting. However, if the contractile activity of muscle is increased, this effect is abated. Because the gene encoding glutamine synthetase is known to be glucocorticoid inducible, it represents an appropriate model for testing whether glucocorticoids and endurance training can exert antagonistic effects on the expression of specific genes in muscle tissue. Our data confirm that administration of hydrocortisone 21-acetate to rats produces 2.4- and 5.9-fold increases in plantaris muscle glutamine synthetase enzyme activity and mRNA, respectively. Moreover, subjecting rats to a 12- to 16-wk exercise program diminishes the basal levels of these indices of glutamine synthetase expression to approximately 60% of the values observed in sedentary controls. Endurance training produces a similar effect on plantaris muscle glutamine synthetase expression in glucocorticoid-treated animals. These data demonstrate that the therapeutic effects of exercise in counteracting muscle atrophy are associated with attenuation of expression of a glucocorticoid-inducible gene in skeletal muscle.