INTESTINAL ISCHEMIA AND REPERFUSION INJURY IN GROWING RATS: HYPOTHERMIA AND N-ACETYLCYSTEINE MODULATION EDNA F.S. MONTERO, M.D., Ph.D.,* MARCOS S. ABRAHA ˜ O, M.Sc., MA ´ RCIA K. KOIKE, Researcher, MO ˆ NICA C.B. MANNA, M.D., AND CARLOS E.B. RAMALHO, M.Sc. 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 rand- omized into 5 groups with 6 animals in each: I/RH group, intestinal ischemia under hypothermia for 40 min and rep- erfusion for 30 min; I/RH-NAC group, same procedure but adding NAC (150 mg Æ kg )1 ), previously with ischemia; S-H group, 1 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, 10). After laparotomy, the superior mesenteric artery was dissected and clamped to promote ischemia. Topic hypothermia was obtained by using plastic bags at 4°C, changed every 10 min. Rats were sacrificed by exsanguination, and blood samples were utilized to measure Dlactate. Intestinal fragments were removed 2 for morphological study. Statistical analysis was done with nonparametric tests (P  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 3 intestinal ischemia and reperfusion were associated to hypothermia (I/RH = 36 mg/dl). NAC de- creased 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 hypo- thermia. However, NAC showed a protective effect on the small bowel from ischemia-reperfusion injury. Para avaliar a lesa ˜o de isquemia e reperfusa ˜o em ratos em crescimento, modulada com a hipotermia (I/RH) e a N-acet- ilcisteı ´na (NAC), foram usados 30 ratos machos, EPM-1 Wistar, com idade de 35 dias, pesando 90 g. Os ratos foram randomizados em 5 grupos com 6 animais cada: grupo I/RH, isquemia intestinal + hipotermia por 40 min e reperfusa ˜o por 30 min; grupo I/RH-NAC, adicionada a ` NAC (150 mg kg )1 ), previamente a ` isquemia; grupo simulado-H, hipotermia to ´ pica por 40 min e observac ¸a ˜ o durante 30 min; grupo I/RH-veı ´culo; e grupo simulado-NAC, administrac ¸a ˜ o de NAC e observac ¸a ˜o por 70 min. Apo ´ s heparinizac ¸a ˜ o, os ratos foram anestesiados com cetamina (60 mg kg )1 ) e xilazina (10 mg kg )1 ), intra- muscular. Os procedimentos operato ´ rios foram realizados com te ´ cnica microciru ´ rgica (aumento, 10). Apo ´ s laparoto- mia, a arte ´ ria mesente ´ rica superior foi dissecada e clampe- ada para promover isquemia. A hipotermia to ´ pica foi obtida por meio de bolsas pla ´ sticas a 4°C, mudadas a cada 10 min. Os ratos foram sacrificados por exsangu ¨ inac ¸a ˜o e amostras de sangue foram utilizadas para medir o D - lactato. Frag- mentos intestinais foram removidos para o estudo mor- folo ´gico. A ana ´ lise estatı ´stica foi feita com teste de Kruskal- Wallis (P  0.05). Com relac ¸a ˜o ao D - lactato, os dados mos- traram lesa ˜o bioquı ´mica, com a hipotermia isoladamente (S- H = 27 mg/dl) que se tornou mais acentuada quando a is- quemia e reperfusa ˜ o intestinal foram associadas (I/RH = 36 mg/dl). A NAC diminuiu a lesa ˜o de isquemia e reperfusa ˜o intestinal (I/RH-NAC = 19 mg/dl). As leso ˜ es morfolo ´ gicas, avaliadas na colorac ¸a ˜ o de HE, mostraram graus 4 e 5 para os grupos I/R H e I/R H-Ve, respectivamente, em contraste com os outros grupos (I/RH-NAC = 2, S-H = 1, e S-NAC = 1). Os achados permitiram concluir que a lesa ˜o de isquemia e rep- erfusa ˜o intestinal ocorreu tanto morfologicamente como funcionalmente, mesmo com a associac ¸a ˜ o da hipotermia, que isoladamente causou lesa ˜o bioquı ´mica. Entretanto, a NAC mostrou um efeito protetor do intestino na lesa ˜o de is- quemia e reperfusa ˜o. ª 2003 Wiley-Liss, Inc. MICROSURGERY 23:517–521 2003 Disciplina de Te ´ cnica Operato ´ ria e Cirurgia Experimental, Departamento de Cirurgia, Escola Paulista de Medicina, Universidade Federal de Sa ˜ o Paulo, Sa ˜ o Paulo, Brazil Grant sponsor: Fundo de Auxı ´lio aos Docentes e Alunos. *Correspondence to: Edna Frasson de Souza Montero, Alameda Espada 134, Alphaville 11, 06540-395 Santana de Parnaı ´ba, Sa ˜ o Paulo, Brazil. E-mail: Efsmontero.dcir@epm.br Received 30 May 2003; Accepted 1 July 2003 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/micr.10163 ª 2003 Wiley-Liss, Inc.