[Effects of insulin glargine at different times on organ oxidative stress in burned rats with delayed resuscitation].

Objective: To examine the antioxidant effect of low dosage insulin glargine intervention at different time in rats with delayed resuscitation after burn, in order to acquire a better time of antioxidant intervention during delayed resuscitation following burn injury. Methods: With 10 rats in each group, 50 male SD rats were assigned to sham injury group, delayed resuscitation group, immediate post-burn insulin glargine treatment group (immediate treatment group), 2 hours post-burn insulin glargine treatment group(2 h treatment group), and 6 hours post-burn insulin treatment group(6 h treatment group) with random number table. Each treatment group received subcutaneous injections of insulin glargine (1.0 U·kg-1·d-1) immediately, two hours and six hours after the burn, while the delayed resuscitation group received the same amount of normal saline six hours after the burn. To imitate delayed fluid resuscitation, the delayed resuscitation group and each therapy group were intraperitoneally injected with normal saline (40 ml/kg) 6 hours after injury. No medicine and fluid resuscitation was administered to the sham injury group. Rats in the sham injury group had their abdominal aortic blood, hearts, and kidney tissues collected immediately after injury, while rats in the other groups had their blood and tissues collected 24 hours later. To analyze the timing of antioxidant intervention, the activities of CuZn-superoxide dismutase (CuZn-SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), xanthine oxidase (XOD) and myeloperoxidase (MPO) in blood glucose and myocardial and renal tissues were measured by spectrophotometry. Results: Compared with the sham group, blood glucose levels in the delayed resuscitation group increased [(10.72±0.80) vs (6.57±0.82)mmol/L,P<0.001], while in the myocardium and kidney, the activities of CuZn-SOD, CAT, GSH-Px and T-AOC decreased (all P<0.05) and the activities of XOD and MPO increased (all P<0.05). Compared with the delayed resuscitation group, blood glucose decreased in the immediate, 2 h, and 6 h treatment groups (all P<0.05). In the immediate and 2 h treatment group, the activities of CuZn-SOD, CAT, GSH-Px and T-AOC in the myocardium and kidney increased(all P<0.05). In the 6 h treatment group, only the activities of GSH-Px in myocardium, CAT and GSH-Px in kidney increased (all P<0.05). Compared with the delayed resuscitation group, in the immediate treatment group, the activities of MPO and XOD in myocardial tissue and XOD in renal tissue decreased (all P<0.05). The activities of MPO and XOD in myocardial and renal tissues of the 2 h treatment group both decreased (all P<0.05). In the 6 h treatment group, the activities of MPO in myocardial tissue and XOD in renal tissue both decreased (all P<0.05). Compared with the immediate treatment group, the activity of GSH-Px in myocardial tissue increased (P<0.05), and the activities of CuZn-SOD, CAT, GSH-Px and T-AOC in renal tissue increased in the 2 h treatment group (all P<0.05). The activities of CuZn-SOD, CAT, GSH-Px and T-AOC in myocardium of 6 h treatment group decreased (all P<0.05). Compared with the immediate treatment group, the activities of XOD and MPO in myocardial tissue and XOD in renal tissue of the 2 h treatment group had no significant difference (all P>0.05), but the activity of MPO in renal tissue decreased (P<0.05). The activities of XOD and MPO in myocardial tissue of the 6 h treatment group increased (all P<0.05). Compared with the 2 h treatment group, the activities of CuZn-SOD, CAT and GSH-Px and T-AOC in myocardium and kidney tissues in the 6 h treatment group decreased (all P<0.05), while the activities of XOD and MPO in myocardium and kidney tissues increased [myocardium: (374±8) vs (290±19) U/g, (0.021 8±0.003 9) vs (0.010 7±0.002 4) U/g, kidney: (157±6) vs (128±9) U/g, (0.026 8±0.004 3) vs (0.013 4±0.003 1) U/g, all P<0.05]. Conclusions: The timing of the intervention is related to the antioxidant effect of insulin glargine during delayed burn resuscitation. The intervention immediately and 2 hours after burn could have a better antioxidant effect compared to the intervention at 6 hours after burn.

[Effects of medium and long-term insulin pretreatment on the activity of main oxidase and antioxidant enzyme in the myocardium of burned rats with delayed fluid resuscitation].

OBJECTIVE: To observe the effects of medium and long-term insulin pretreatment on the activity of main oxidase and antioxidant enzyme in the myocardium of burned rats with delayed fluid resuscitation. METHODS: According to random number table method, forty male Sprague-Dawley (SD) rats were divided into pseudo-burn group, burn delayed resuscitation group, insulin glargine pretreatment group and neutral protamine hagedorn (NPH) insulin pretreatment group, with 10 rats in each group. 30% total body surface area (TBSA) as III degree scald model was prepared by bathing the back of rats in 95 centigrade hot water for 15 s; the rats in the pseudo-burn group were immersed in 37 centigrade warm water for 15 s as control. Insulin glargine pretreatment group, NPH insulin pretreatment group and burn delayed resuscitation group were injected subcutaneously with insulin glargine, NPH insulin, and normal saline 1.0 U×kg-1×d-1 2 hours after injury, and intraperitoneal injection of normal saline 40 mL/kg simulated delay resuscitation 6 hours after injury. The pseudo-burn group didn't receive medicine and delayed resuscitation. Abdominal aortic blood samples and heart tissue were collected immediately after simulating scald in the pseudo-burn group, and 24 hours after scald in three burn groups. Blood glucose, xanthine oxidase (XOD), myeloperoxidase (MPO), CuZn-superoxide dismutase (CuZn-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) of the heart tissue were determined by spectrophotometry. RESULTS: Compared with the pseudo-burn group, the burn delayed resuscitation group have significantly higher blood glucose level and the XOD and MPO in the heart tissue, while significantly lower CuZn-SOD, CAT, and GSH-Px in the heart tissue. Compared with the burn delayed resuscitation group, insulin glargine pretreatment group and NPH insulin pretreatment group have lower blood glucose level and heart tissue XOD [blood glucose (mmol/L): 6.37±1.22, 6.66±1.45 vs. 9.47±0.80; XOD (U/g): 271.93 (261.59, 275.91), 285.32 (251.96, 297.29) vs. 363.37 (354.12, 377.76), all P < 0.05], while significantly higher heart tissue CuZn-SOD, CAT, and GSH-Px [CuZn-SOD (U/g): 0.13±0.01, 0.14±0.01 vs. 0.10±0.01; CAT (U/g): 29.17±7.28, 27.16±7.37 vs. 18.36±4.53; GSH-Px (U/g): 0.33 (0.16,0.41), 0.30 (0.17,0.41) vs. 0.07 (0.04,0.11), all P < 0.05]. MPO activity in insulin glargine pretreatment group was significantly lower than that in burn delayed resuscitation group (U/g: 0.016±0.002 vs. 0.020±0.002, P < 0.05), but there was no significant difference between insulin pretreatment group and NPH insulin pretreatment group (U/g: 0.019±0.003 vs. 0.020±0.002, P > 0.05). There was no significant difference in the blood glucose, and activities of XOD, MPO, CAT, GSH-Px between insulin glargine pretreatment group and NPH insulin pretreatment group, but the activity of CuZn-SOD in NPH insulin pretreatment group was further higher than that in insulin glargine pretreatment group (U/g: 0.14±0.01 vs. 0.13±0.01, P < 0.05). CONCLUSIONS: Medium and long-term insulin pretreatment can improve the antioxidant capacity of myocardium in delayed resuscitation rats after burns, inhibit the production of reactive oxygen species and improve the scavenging capacity of reactive oxygen species. However, only CuZn-SOD activity is different between the two groups, and further study needs to be carried out to determine whether it is related to the type if insulin.