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 ℃ hot water for 15 s; the rats in the pseudo-burn group were immersed in 37 ℃ 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.