Influence of burn injury on protein metabolism in different types of skeletal muscle and the role of glucocorticoids.
BACKGROUND
Negative nitrogen balance after burn injury mainly indicates muscle catabolism, but the exact influence of burn on protein synthesis and breakdown in different types of skeletal muscle and the role of glucocorticoids in this metabolic response are unknown.


METHODS
A 30 percent body surface area flame burn was inflicted on rats. Protein turnover rates were measured in vitro in the white fast-twitch extensor digitorum longus (EDL) muscle and the red slow-twitch soleus muscle. To test the role of glucocorticoids, groups of rats were treated with the glucocorticoid receptor antagonist RU 38486 or vehicle.


RESULTS
Burns resulted in reduced protein synthesis and stimulated protein breakdown, in particular myofibrillar protein breakdown, and the changes were substantially more pronounced in the EDL than in the soleus muscle. A burn-induced increase in muscle proteolysis was abolished by treatment with RU 38486, whereas the reduced protein synthesis was not affected by the glucocorticoid receptor antagonist.


CONCLUSIONS
The results suggest that the white fast-twitch muscle is more sensitive to the effects of burn injury than the red slow-twitch muscle. Burn-induced muscle proteolysis may be mediated, at least in part, by glucocorticoids, whereas protein synthesis is probably regulated by other mechanisms.
Fang
C H
CH
Department of Surgery, University of Cincinnati, OH.
James
H J
HJ
Ogle
C
C
Fischer
J E
JE
Hasselgren
P O
PO
D000818:Animals; D001415:Back; D002056:Burns / Q000378:metabolism / Q000503:physiopathology*; D005121:Extremities; D008297:Male; D015735:Mifepristone / Q000494:pharmacology*; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
D009124:Muscle Proteins; D015735:Mifepristone