Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Objectives: To characterize the pulmonary and systemic inflammatory responses of rats undergoing 1-hour or 3-hour one-lung ventilation (OLV) with subsequent 1-hour lung re-expansion. Design: A prospective, randomized, controlled animal experiment. Setting: University laboratory. Participants: Thirty male Wistar rats were used. Interventions: Rats were subjected to 1- or 3-hour OLV followed or not by 1-hour lung re-expansion. Control rats received no ventilation. Measurements and Main Results: Pulmonary protein extravasation, pulmonary myeloperoxidase (MPO) activity, cytokine levels in serum and bronchoalveolar lavage (BAL), counts of total and differential cells in BAL fluid, gasometric data, and mean arterial blood pressure (MABP) were all evaluated. Bronchial occlusion for 1 or 3 hours with no lung re-expansion did not significantly change the protein extravasation in the right and left lungs compared with the control group. However, rats submitted to 1- or 3-hour OLV followed by lung re-expansion exhibited pulmonary edema formation and neutrophil recruitment as well as a higher MPO activity in comparison with control rats. Increased levels of interleukin (IL)-6, IL-1 beta, and tumor necrosis factor-alpha in BAL fluid were observed. Increased levels of IL-6 and IL-10 in serum also were detected. Blood gas and MABP did not differ between groups. Conclusions: Lung re-expansion after bronchial occlusion evokes an acute lung inflammatory response, which has been shown to be more pronounced in long periods of bronchial occlusion in terms of cytokine inflammatory response. In addition, the magnitude of this inflammatory response also can be detected systemically. (C) 2012 Elsevier Inc. All rights reserved.263427432Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)