Androgen cytosol binding in exercise-induced sparing of muscle atrophy.
This study was undertaken to determine whether the exercise-induced sparing of glucocorticoid-induced muscle atrophy is related to increased androgen cytosol binding. Female rats were divided into a sedentary or an exercise group that was trained by treadmill running 100 min/day for 13-15 wk. During the last 12 days of training, each of these groups was further subdivided into groups that received daily subcutaneous injections of cortisone acetate (CA) (100 mg/kg body wt) or the vehicle 1% carboxymethyl cellulose. Exercise prevented 30-40% of the weight loss due to CA treatment in gastrocnemius and plantaris muscles. Scatchard analyses of specific binding of [3H]methyltrienolone (R1881), a synthetic androgen that binds to androgen receptors, were nonlinear in muscles from vehicle-treated sedentary and trained rats and were resolved by a two-component binding model. The lower affinity component, which was attributed to a glucocorticoid receptor, disappeared in muscles of glucocorticoid-treated animals as evidenced by linear Scatchard plots. Receptor concentrations of the androgenic component of [3H]methyltrienolone binding were similar in gastrocnemius and plantaris muscles in all treatment groups. In binding specificity studies of gastrocnemius muscles, the relatively high competition by various glucocorticoids and progesterone for [3H]methyltrienolone binding in the vehicle-treated groups was reduced by CA treatment. The lack of change in androgen cytosol receptor levels suggests that this is not a mechanism by which exercise protects against glucocorticoid-induced muscle atrophy.
D000728:Androgens / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D003348:Cortisone / Q000031:analogs & derivatives / Q000633:toxicity; D003600:Cytosol / Q000378:metabolism; D004963:Estrenes / Q000378:metabolism; D005260:Female; D015741:Metribolone; D009133:Muscular Atrophy / Q000139:chemically induced / Q000378:metabolism*; D005082:Physical Exertion; D051381:Rats; D011919:Rats, Inbred Strains; D011944:Receptors, Androgen / Q000378:metabolism*; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D011987:Receptors, Steroid / Q000378:metabolism*; D045165:Testosterone Congeners / Q000378:metabolism
D000728:Androgens; D004963:Estrenes; D011944:Receptors, Androgen; D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D045165:Testosterone Congeners; D015741:Metribolone; D003348:Cortisone