Effect of thermal injury on glucocorticoid and androgen binding in skeletal muscles with different fiber populations.
The role of glucocorticoids and androgens in postburn augmentation of skeletal muscle proteolysis was investigated following a 3-second single hindlimb scald (6 to 7% body surface area) in the rat. Soleus muscles and calf muscles from the burned and unburned hindlimbs were excised 3 days postburn and compared to age-matched controls to evaluate both the local and systemic effects of burn injury. Free tyrosine content in soleus and calf muscles of the burned limb was 30% and 58%, respectively, higher than in corresponding control muscles. Net proteolysis in burned limb soleus muscles, as measured by tyrosine "production' in vitro, was more than doubled as compared to controls. In contrast, tyrosine content and production by muscles from the unburned limb of burned rats dis not differ from controls. Specific binding of the glucocorticoid dexamethasone in cytosols of burned limb soleus and calf muscles was more than 80% below control level. Soleus muscles from the unburned limb of burned rats showed a 60% decrease in dexamethasone binding but that of the unburned limb calf muscles did not differ from controls. The latter difference and the observation in control rats of a relatively lower dexamethasone binding in calf muscles as compared to soleus muscles suggest that the glucocorticoid binding could be influenced by the type of fibers comprising the muscle. Unlike the glucocorticoid binding, neither the thermal injury nor the muscle fiber type had a significant effect on specific cytosolic binding of the androgen methyltrienolone by the muscle tissues studies. It is concluded that thermal injury restricted to one hindlimb leads to regional differences in skeletal muscle proteolysis and glucocorticoid binding. Muscles of the burned region exhibit stimulation of proteolysis and virtual disappearance of cytosolic glucocorticoid receptors. Muscles from the unburned region appear to have a normal rate of proteolysis and either normal or decreased glucocorticoid binding. It remains to be elucidated whether the decrease in cytosolic glucocorticoid receptors is due to changes in receptor synthesis and degradation, or to accelerated translocation of the receptors into the nucleus.
D000728:Androgens / Q000378:metabolism*; D000818:Animals; D002056:Burns / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism*; D008297:Male; D009132:Muscles / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011919:Rats, Inbred Strains; D014443:Tyrosine / Q000378:metabolism
D000728:Androgens; D005938:Glucocorticoids; D014443:Tyrosine