Comparisons of pulmonary lesion and changes in surfactant proteins A and B induced by seawater and freshwater immersions after open chest injury in dogs

Objective To compare the extent of acute lung injury (ALl) and changes in surfactant proteins A (SP-A) and B (SP-B) induced by seawater and freshwater immersion following open chest injury in dogs. Methods The animal model was established by seawater and freshwater injection into the thoracic cavity after open chest injury. All the experimental animals were observed for 6 hours, during which blood gas analysis, levels of TNF-α and IL-8, contents of SP-A and SP-B in the lung and blood serum were measured at different time points. Pulmonary histopathology and SP-B immuno-histochemistry were measured after the animals were sacrificed at the end of the experiment. Results Both seawater immersion and freshwater immersion could induce hypoxemia, with the extent of hypoxemia for the seawater immersion group (SG) being obviously much severer than that of the freshwater immersion group (FG) (P < 0.05). The levels of IL-8 and TNF-α in blood serum and BALF of both experimental groups were significantly higher than those of the control group (CG) (P<0.05). Pulmonary pathological lesion was noted in both SG and FG, with that of SG being severer than that of FG. The levels of SP-A and SP-B in BALF in SG and FG all decreased significantly(P <0.05) ,while the levels of SP-A and SP-B in blood serum increased gradually (P < 0.05). Type Ⅱ alveolarepithelial cells with SP-B positive in the lung decreased in both experimental groups, with grey scale values being significantly lower than that of CG. And significant deviation was observed between SG and FG (P <0.05). Conclusions Pulmonary lesion induced by seawater immersion after open chest injury was severer than that induced by freshwater immersion. Key words: Acute lung injury; Seawater immersion;  Freshwater immersion; Surfactant protein-A; Suffactant protein-B