RESUMO
OBJECTIVE: To evaluate the influence of recruitment maneuver (RM) on alveolar epithelium barrier in rat with acute lung injury (ALI). METHODS: The ALI rats model were replicated by lipopolysaccharide iv injection. Sustained inflation (SI), as a method of RM, was applied by airway pressure of 30 cm H(2)O for 30 seconds. Forty-eight male SD rats were randomly divided into four groups: normal group, ALI group, low tidal volume (V(T)) group (LV group) and low V(T)+SI group (SI group). After 4 hours of mechanical ventilation, lung injury was evaluated by Smith lung injury score. Extravascular lung water (EVLW) was measured by gravimetric method. Alveolar epithelium apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL). mRNA expression of surfactant protein (SP)-C was assessed by reverse transcription polymerase chain reaction (RT-PCR). Interleukin (IL-6) and IL-10 levels in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Injury degree of lung tissues in SI group was lighter than those of ALI and LV groups under microscope. A few of apoptotic epithelial cells were observed in SI group (all P<0.05). Compared with LV group, apoptotic epithelial cells were decreased in number in SI group. Smith lung injury score and EVLW in ALI, LV and SI group were higher than those in the control group. Smith lung injury score in ALI group was significantly higher than the score in SI and LV group (both P<0.05). Smith lung injury score and EVLW of SI group were significantly lower than those of LV group (both P<0.05). There was no significant difference in EVLW between SI and ALI group. The SP-C mRNA expression was significantly lowered in ALI, LV and SI groups compared with that in control group (all P<0.05). The SP-C mRNA expression in SI group was stronger than LV group significantly (P<0.05), but not significant when compared with that of ALI group. The concentrations of IL-6 and IL-10 in BALF of ALI, LV and SI groups were significantly higher than those of control group (all P<0.05). In SI group, the concentration of IL-6 in BALF was lower than LV group (P<0.05). There was no difference in the permeability of alveolar epithelium among ALI, LV and SI groups. CONCLUSION: RM can alleviate lung tissue injury, up-regulate SP-C mRNA expression in alveolar epithelium, protect alveolar epithelium barrier and down-regulate pulmonary inflammatory mediator expression in ALI.
