Regulation on the expression of Clara cell secretory protein in the lungs of the rats with acute lung injury by growth hormone

Background Clara cell secretory protein （CC16） is an important lung derived protective factor and may play an important role on the pathogenesis of acute lung injury （ALl） induced by endotoxemia. Growth hormone （GH） is an important anabolism hormone secreted by GH cells of the hypophysis. Previous research showed that GH would significantly exacerbate ALl induced by endotoxemia, but the mechanism is not very clear yet. Whether the effects are related to CC16 or not is undetermined. Methods One hundred and twelve male Sprague-Dawley rats were randomly divided into an ALl group and a GH group. The rats in the two groups were subdivided into seven subgroups, according to injection with lipopolysaccharides （LPS） or not, then according to different intervals of time after LPS injection; 0 hour （pre-injection of LPS, acted as control group）, 0.5 hour, 1 hour, 2 hours, 4 hours, 6 hours and 24 hours for subgroups. Pulmonary alveolar septa area density （PASAD） and ploymorphonuclear cells （PMN） in the lungs were analyzed morphometrically. The levels of tumor necrosis factor （TNF） and interleukin 6 （IL-6） were determined by radioimmunoassay. To analyze the expression and activation of nuclear factor kappa B （NF-KB）, the numbers of NF-KB positive cells in lungs were counted after immunofluorescence staining, and the levels of NF-KB inhibitory protein-a （IKB-a） in lung homogenates of rats were detected by Western blotting. The expression levels of CC16 mRNA in lungs of the rats with ALl were determined by semi-quantitative reverse transcription polymerase chain reaction （RT-PCR）. The levels of CC16 protein in lung homogenates were detected by Western blotting. Results Half an hour after LPS injury both the PASAD and PMN numbers in lungs of the rats with ALl began to increase significantly and peaked at 6-hour post-injury. They then began to recover and reached normal levels at 24-hour post-injury. Both the PASAD and PMN numbers in the GH group increased more significantly than those in the ALl group. The levels of TNF in lungs of the rats with ALl homogenates increased significantly 0.5-hour post-injury, peaked at 1-hour and maintained a high level until 6 hours then gradually recovered. The content of TNF in the GH group lung homogenates increased more significantly than in the ALl group post-injury. The contents of IL-6 in rat lung homogenates began to increase significantly at 1-hour post-injury, peaked at 4 hours then gradually returned to normal levels by 6 hours