[Effect and mechanism of dantrolene on skeletal muscle of rats with severe scald injury].
OBJECTIVE
To explore the effect and mechanism of ryanodine receptor antagonist dantrolene on skeletal muscle of rats with severe scald injury.


METHODS
A total of 56 Wistar rats were divided into control, scald and dantrolene treatment groups according to a random digital table. Rats in scald and dantrolene treatment groups were subject to 50% total body surface area (TBSA) full-thickness scald by a 12-second immersion of back and a 6-second immersion of abdomen in 94 °C water and then received an intraperitoneal injection of Ringer's solution. At the same time, the rats in scald group received 5% mannitol through caudal vein while those in dantrolene treatment group received dantrolene 2 mg/kg (dissolved in 5% mannitol). Rats in control group were sham-injured through an immersion of back and abdomen into 37 °C warm water. Tibialis anterior muscle samples were harvested at Days 1, 4 and 7 post-scalding. Changes of skeletal muscle ultrastructure were observed by transmission electron microscope, subcellular calcium ion (Ca(2+)) contents of skeletal muscle (including cytoplasm, mitochondria & sarcoplasm reticulum) were detected by electron probe X-ray microanalysis (EPMA) and the levels of calpain-1 and calpain-2 protein were determined by Western blot. And the activities of calpain were detected by enzyme-linked immunosorbent assay.


RESULTS
In scald group, assorted arrangement appeared immediately at Day 1 post-injury and partial disappearance of Z lines at Day 7 post-injury. There were no significant ultrastructure changes in dantrolene treatment group at Day 1 and 4 post-injury. Curled filament and mild fracture occurred merely in dantrolene treatment group at Day 7 post-injury. The cytoplasmic contents of Ca(2+) were significantly higher in scald group than those in control group at Day 1 and 4 ((0.964 ± 0.060), (0.639 ± 0.067) vs (0.266 ± 0.029) µmol/L respectively, all P < 0.05) while the contents of Ca(2+) within sarcoplasm reticulum were obviously lower in scald group than those in control group at Day 1 and 4 ((0.368 ± 0.060), (0.814 ± 0.089) vs (1.337 ± 0.112) µmol/L respectively, all P < 0.05). However, those subcellular regions in dantrolene treatment group ((0.310 ± 0.069), (0.490 ± 0.039) and (1.241 ± 0.073), (1.161 ± 0.094) µmol/L) had no significant difference with control group (all P > 0.05). Calpain-1 and calpain-2 protein levels in scald group increased significantly at Day 1 and 4 post-injury versus control group (1.371 ± 0.034, 1.214 ± 0.030 vs 0.838 ± 0.017 & 1.464 ± 0.015, 1.390 ± 0.023 vs 0.806 ± 0.026 respectively, all P < 0.05), whereas calpain-1 and calpain-2 protein levels in dantrolene treatment (0.984 ± 0.031, 0.935 ± 0.023 and 0.836 ± 0.014, 0.741 ± 0.020) obviously were lower than those in scald group respectively (all P < 0.05). The activities of calpain in scald and dantrolene treatment groups at Day 1, 4 and 7 post-injury were (8.33 ± 0.21), (9.33 ± 0.21), (10.59 ± 0.18) and (7.76 ± 0.28), (7.86 ± 0.20), (7.91 ± 0.22) µmol/L respectively while the activity of calpain in control group was (7.62 ± 0.19) µmol/L. The activities of calpain in scald group were significantly higher than those in dantrolene treatment and control groups (all P < 0.05) whereas the activities of calpain in dantrolene treatment group had no obvious change versus control group (all P > 0.05).


CONCLUSIONS
Dantrolene offers significant protection from skeletal muscle tissue damage and minimizes the ultrastructural change of tibialis anterior muscle induced by severe scald injury. The mechanism is probably through inhibiting an excessive release of Ca(2+) within sarcoplasm reticulum and down-regulated cytoplasmic expression and activity of calpain-1 and calpain-2.
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China.
Li
L
Ma
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China. Email: cjk304@126.com.
Jiake
J
Chai
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China.
Wanli
W
Chu
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China.
Hongjie
H
Duan
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China.
Dawei
D
Li
Department of Burns & Plastic Surgery, First Affiliated Hospital, General Hospital of PLA, Beijing 100048, China.
Yonghui
Y
Yu
D000818:Animals; D002056:Burns / Q000188:drug therapy / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology* / Q000627:therapeutic use; D004195:Disease Models, Animal; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar
D002154:Calpain; D003620:Dantrolene; D002118:Calcium