Change of alveolar epithelial type II cells and pulmonary surfactant protein A in young rats with acute lung injury

Objective To study the temporal changes of alveolar epithelial type Ⅱ cells and surfactant pro-tein A in young rats with acute lung injury induced by lipopolysaecharide. Method Totally 110 SD young rats (male:53, female : 57) were randomly divided into ALI and normal control groups (six subgroups in each group).LPS(4 mg/kg) was given intraperitoneally in ALI group. The same amount of normal saline was given in the con-trol groups. Eight rats in each subgroup were sacrificed at 6, 12, 24, 36, 48 and 72 hours after the injection.Lung samples were taken for transmission electron microscope examination. RT-PCR was epmloyed for the mea-surement of SP-A mRNA. Western blot was used for the detection of SP-A in the lung tissue. ANOVA and homo-geneity of variance test were performed by SPSS 12.0. Results The microvilli disappeared at 24 hours after the injection of LPS. The number of lamellar body (LBs) was provisionality increased at 24 hours and 48 hours. The ring-like an'angement of LBs around nucleus and the giant LB with vacuole-like deformity were found as the main characteristics of AEC- Ⅱ in ALI at 48 hours. The number of LBs reduced and broken and residual LB remained at 72 hours. SP-A elevated greatly from 24 to 48 hours (P < 0.01), reached peak at 36 hours (6.94 ± 0.80, P <0.01),reached the lowest level(3.87 ±0.50, P <0.01)at 72 hours. Conclusions The pathological changes of AEC-Ⅱ and SP-A in lung tissue wiht ALI are time-dependent. The typical alterations of AEC- Ⅱ occurs at 48 hours accompanied by the compensatory increase of SP-A. AEC- Ⅱ is seriously injuried with the typical changes of LBs and the diminishing of SP-A in lung tissue. Key words: Acute lung injury;  Lipopolysaccharide;  Alveolar epithelial type Ⅱ cell;  Lamellar body;  Sur-factant protein A