Expression Of PEPT2 MRNA In The Lung Of Rat With Lipopolysaccharide-induced Acute Lung Injury

Objective To investigate the expression of PEPT2 mRNA in the lung of rat with lipopolysaccharide(LPS)-induced acute lung injury. Methods Healthy adult Spragne-Dawley rats (200±20g, ♀: ♂ =1:1) were divided randomly into five groups (n = 8 per group): control,saline, LPS 2 h, LPS 4 h, or LPS 8 h. Animals in control group did not receive any treatment. Animals in saline group received 0.2 ml sterile saline and were killed after 2h. Animals in the three LPS groups received 0.5 mg/kg of LPS intratracheally, and were killed after 2 h, 4 h and 8 h. Tissue sections were stained with hematoxylin and eosin and examined under light microscope to observe lung histophathological changes. Lung W/D ratios were measured. Total protein concentration in BALF was measured using the Folin-phenol Method. Lung MPO activity was measured by MPO assay kit. The expression levels of PEPT2 mRNA were evaluated by semiquantitative RT-PCR. The statistical analysis was carried out using SPSS 12.0 for Windows. Data were statistically analyzed using a one-way analysis of variance followed by the Dunnett's multiple comparison test. P <0.05 was considered statistically significant. Results Histopathological evaluation: Typical pathological inflammation changes in the lung were observed in LPS groups, including alveolar congestion, hemorrhage, edema, infiltration of neutrophils in the airspace or vessel wall, thickness of the alveolar wall, and hyaline membrane formation. Lung W/D ratios: The lung W/D ratios in LPS 2 h, LPS 4 h and LPS 8 h group were significantly higher than those in control group and saline group (P < 0.01). The lung W/D ratios significantly increased at 2 h, peaked at 4 h and then remained stable to 8 h after LPS instillation. Total protein content in BALF: Compared with control group and saline group, total protein concentration in BALF in LPS 2h group increased significantly (P< 0.05), total protein concentration in BALF in LPS 4 h and LPS 8 h group was significantly higher than that in control group, saline group and LPS 2h group( P < 0.01). Total protein concentration in BALF increased at 2 h after LPS instillation , and increased continuously to 8 h after LPS instillation. Lung MPO activity: The lung MPO activity in LPS 2 h, LPS 4 h and LPS 8 h group was significantly higher than that in control group and saline group (P < 0.01). The lung MPO activity significantly increased at 2 h after LPS instillation, reached the maximum at 4 h and then remained stable to 8 h. Semiquantitative RT-PCR : Compared with control group and saline group, there was no statistical difference in PEPT2 mRNA levels in the lung of rats in LPS groups(P > 0.05).Conclusions ① A single intratracheal instillation of 0.5 mg/kg of LPS can induce successfully acute lung injury rat model. (2) PEPT2 mRNA levels do not change significantly in the lung of rat with LPS-induced acute lung injury.