OBJECTIVETo investigate changes in apoptosis-related ligands in serum in rats with severe scald and the effect of intensive insulin therapy on the changes.

METHODSOne hundred and fifty Wistar rats were randomly divided into 3 groups: sham burn (SB), scald (S) and treatment (T) groups. Rats in S and T groups were inflicted with 40% TBSA full-thickness burn, followed by intraperitoneal injection with 40 mL/kg of isotonic saline for resuscitation. Rats in T group were subcutaneously injected insulin in a dose of 0.25 U/100 g 24 hours after burn injury, and every 12 hours for 5 days (0.25, 0.50, 0.75, 1.00, 1.25 U/100 g each day, respectively) to control the level of blood glucose between 3 and 6 mmol/L. Rats in SB group were sham scalded at 37 degrees C without resuscitation. Blood was drawn from abdominal aorta on 1, 4, 7, 10, 14 post burn day (PBD) for determination of serum levels of TNF-alpha, soluble Fas ligand (sFasL) and soluble Fas receptor (sFas) by enzyme-linked immunosorbent assay (ELISA), and insulin by radioimmunity assay (RIA).

RESULTSThe serum level of TNF-alpha in S group peaked on 1 PBD (30.9 +/- 8.7) ng/L, which showed statistically significant difference when compared with that of SB and T groups (12.7 +/- 2.8) ng/L, (16.8 +/- 4.7) ng/L, respectively, P < 0.01), then lowered gradually to become similar to that of SB group on 7 PBD. The level of TNF-alpha in T group increased gradually, but was obviously lower than that of S group on 1, 4, 7 PBD (P < 0.01). The level of sFasL in S (on 7-14 PBD) and T (4-10 PBD) groups was significantly higher than that in SB group (P < 0.05), then lowered to normal level. The levels of sFas on 4-10 PBD in T group were obviously higher than that in S and SB group (P < 0.05). Ratio of sFasL to sFas in serum of S group was higher than that in SB group on 7, 10 PBD, which was higher than that in T group on 7 PBD (P < 0.05). There was significant decrease in serum level of insulin in S group compared with that of SB group on 4-10 PBD (P < 0.05). The level of insulin in T group increased on 1 PBD, peaked on 4 PBD (327 +/- 15 microU/mL), which was significantly higher than that in SB and S groups (42 +/- 15, 28 +/- 10 microU/mL, respectively, P < 0.01), then decreased gradually to normal level.

CONCLUSIONSInsulin may inhibit apoptosis after burn by down-regulating secretion of apoptotic ligands.