OBJECTIVETo investigate the effects of smoke inhalation injury on the phagocytic function of rat alveolar macrophages and neutrophil apoptosis.

METHODSWistar rats inflicted with smoke inhalation injury were employed in the study. Fifty-four Wistar rats were randomly divided into normal control (N, n = 6) and inhalation injury (I, n = 48) groups. Alveolar macrophages were harvested from the BALF (bronchoalveolar lavage fluid) in I group of rats at 2, 6, 12 and 24 postburn hours (PBHs) and on 2, 3, 4 and 5 postburn days (PBDs). The dynamic change in the phagocytosis of chicken erythrocytes by alveolar macrophages in vitro was observed. The positive rate of myeloperoxidase (MPO) staining of alveolar macrophages (AMs) by MPO staining method was observed, so as to indirectly reflect neutrophil apoptosis and the phagocytosis o apoptotic neutrophils by AMs. Furthermore, the dynamic change in the inflammatory cell apoptosis within BALF was monitored by flow cytometry.

RESULTS(1) he phagocytosis of chicken erythrocytes by AMs was decreased during early postburn stage (2 - 6 PBHs) but recovered after 12 PBHs. (2) The positive MPO staining of AMs was increased gradually after injury and reached top level at 24 PBHs, but decreased during 2 - 5 PBDs. (3) The apoptotic rate within BALF was around 3.02% - 12.95% and rose to peak value at 24 PBHs.

CONCLUSIONThere was increased apoptosis of inflammatory cells within BALF. The resolution process of inflammation after smoke inhalation injury involved neutrophil apoptosis and the phagocytosis of apoptotic neutrophils by AMs.