Posttranslational modifications of cardiac and skeletal muscle proteins byreactive oxygen species after burn injury in the rat

Objective To determine the involvement of oxidative damage in muscle wastin g after burn injury. Summary Background Data Burn injury damages tissue at the site of the burn and also affects peripheral tissue. There is evidence to suggest that react ive oxygen species may be generated in increased amounts after burn, and th ese may contribute to wound healing and to posttranslational modifications of tissue constituents distant from the wound site. Methods The oxidation of muscle proteins was assessed, using the dinitrophe nylhydrazine assay for carbonyl content, in muscles of rats after a full-th ickness skin scald burn covering 20% of the total body surface area, over a 6-week period. In this model, rats failed to incur normal body weight or m uscle weight gain. Results Soleus, extensor digitorum longus, diaphragm, and heart ventricle p roteins were oxidatively damaged after injury. The extent of tissue protein oxidation, however, differed depending on the time points studied. In gene ral, higher levels of protein carbonyl group formation, an indicator of oxi dative damage, were found to occur within 1 to 5 days after injury, and the oxidized protein content of the various tissues decreased during the later stages. Both sarcoplasmic and myofibrillar car; bonyl-containing proteins accumulated in diaphragm 3 days after burn injury and were rapidly removed from the tissue during a 2-hour in vitro incubation. This coincided with in creased proteolytic activity in diaphragm. Conclusions These observations suggest that the loss of proteins modified b y reactive oxygen species may contribute to the burn-induced protein wastin g in respiratory and other muscles by a proteolytically driven mechanism.