[Preliminary study of skeletal muscle apoptosis after severe thermal injury in rats]

To investigate changes in skeletal muscle apoptosis after a severe thermal injury in rats.

One hundred Wistar rats were randomly divided into two groups: sham thermal injury group and severe thermal injury group. They were subdivided into 1, 4, 7, 10, 14 days post-injury with 10 rats in each subgroup. Rats in severe thermal injury group were subjected to a 40% total body surface area full-thickness scald injury. Both weight and tibialis anterior (TA) mass of rats were weighed on 1, 4, 7, 10, 14 days post-injury. Electron microscope was used for observing ultrastructural changes in skeletal muscle, including apoptosis. Tissues of tibialis anterior from burn and sham burn animals were then examined by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and immunohistochemistry.

Compared with sham thermal injury group, body weight and TA mass of rats were decreased from first day on, and it dropped to the lowest level at 4 days (P<0.05 and P<0.01), and started to regain from 7 days on (all P<0.01). Electron micrographs showed condensation of chromatin around the periphery of the nucleus, blebbing of the sarcolemma, and free of myofibrils near myonuclei in a large area in skeletal muscle of thermally injured rats. Sporadic TUNEL positive myonuclei were also seen under light microscope in skeletal muscle in thermal injury group. There were no characteristic signs of apoptosis in skeletal muscle in rats of sham group.

There are skeletal muscle apoptosis after severe thermal injury. It may contribute to atrophy of skeletal muscle after burn injury in rats.