Intestinal ischemia and reperfusion injury in growing rats: hypothermia and N-acetylcysteine modulation.

Our objective was to evaluate intestinal ischemia-reperfusion injury in growing rats, modulated by hypothermia (I/RH) and N-acetylcysteine (NAC). We used 30 EPM-1 Wistar male rats, aged around 35 days, weighing 90 g. Rats were randomized into 5 groups with 6 animals in each: I/RH group, intestinal ischemia under hypothermia for 40 min and reperfusion for 30 min; I/RH-NAC group, same procedure but adding NAC (150 mg x kg(-1)), previously with ischemia; S-H group, topic hypothermia for 40 min, and observation for 30 min; I/R H-Ve group; and S-NAC group, NAC administration and observation for 70 min. All animals were heparinized and anesthetized with ketamine (60 mg kg(-1)) and xylazine (10 mg kg(-1)) intramuscularly. Surgical procedures were done under microsurgical technique (augmentation, 10x). After laparotomy, the superior mesenteric artery was dissected and clamped to promote ischemia. Topic hypothermia was obtained by using plastic bags at 4 degrees C, changed every 10 min. Rats were sacrificed by exsanguination, and blood samples were utilized to measure D(-)lactate. Intestinal fragments were removed for morphological study. Statistical analysis was done with nonparametric tests (P <or= 0.05). Concerning to D(-)lactate, the data showed biochemical tissue injury, with hypothermia only (S-H = 27 mg/dl), and this became more important when intestinal ischemia and reperfusion were associated to hypothermia (I/RH = 36 mg/dl). NAC decreased ischemia-reperfusion injury (I/RH-NAC = 19 mg/dl). Morphologic tissue injuries, evaluated by hematoxylin-eosin staining, showed grades 4 and 5 for the I/RH and I/RH-Ve groups, respectively, in contrast with other groups (I/RH-NAC = 2, S-H = 1, and S-NAC = 1). Based on our data, we conclude that intestinal ischemia reperfusion injury occurred morphologically as well as functionally, even under hypothermia. However, NAC showed a protective effect on the small bowel from ischemia-reperfusion injury.