The Effect Of Whole Lung Lavage On The Rabbit’s Alveolar Epithelial Barrier And The Expression Of AQP1

Objective: To observe the effect of Whole Lung Lavage(WLL)on the rabbit’s alveolar epithelial barrier and the expression of aquaporin1(AQP1), and whether β2agonists could promote the eliminating of the residuallavage fluid resulting from whole lung lavage. Methods:15rabbits wererandomly divided into control group, WLL group, WLL plus β2agonist group(β2agonist group),5rabbits in each group. For the control group, rabbits, undergeneral anesthesia and after tracheotomy, were intubated with the baby-sizeendobronchial tube, separated the left and right lung, the right lung spontaneousbreathing and the left lung without WLL. For the WLL group, according to themethods of WLL in clinic, all the rabbits, under general anesthesia, aftertracheotomy, were intubated with the baby-size endobronchial tube, separatedthe left and right lung, the right lung spontaneous breathing and the left lungwere lavaged with37℃saline.10mL/kg each time, lasting for1-2minutes, thendrainaging for2-3minutes, continuous lavaging for10times, and make sure therecovery rate of lavage fluid was higher than90%. The method of WLL groupwas used for the β2agonist group, with the lavage fluid mixed with0.05mg/kgβ2agonist Terbutaline. Blood gas analysis of the blood from femoral artery wastaken before the examnation and10minutes after lavaging. The rabbits weresacrificed by blood-letting after the examnation, and hematoxylin and eosin(HE)staining and pathological score were used to observe the morphological change of left lungs. Electron microscopic was used to observe the alteration of tightjunctions on the alveolar epithelial barrier. Expression of AQP1protein in lungtissue was detected by immunohistochemical staining. Quantitative real-timePCR was used to detect the expression of AQP1mRNA. SYBR-green I asfluorescent indicator was used to detect the relative expression quantity contentof AQP1. The expression of target gene(AQP1mRNA) was calculated by deltadelta cycle threshold(ΔΔCt) method. The statistical data analyses wereperformed by using SPSS17.0statistical processing software. All measure-ment data was expressed by mean±SD(x±s). The differentces between groupswere analyzed by One-Way ANOVA and Newman-keuls method. Student-Newman-Keuls(SNK) was performed to determine the statistical significanceof groups. P＜0.05was considered signicant difference. Results：(1) Blood gasanalysis before the lavage: Control group [Arterial Partial Pressure ofoxygen(PaO2)6.20±3.12/oxygenation index295.62±14.87], WLL group(PaO25.40±4.84/FiO2311.43±23.06), β2agonist group(PaO269.10±12.43/FiO2329.05±59.20). There were no significant differences in PaO2and oxygenationindex among these three groups (P＞0.05). After WLL, PaO2(48.98±4.01) andoxygenation index(233.24±19.09) of WLL group were obviously lower thanthose of control group(PaO259.22±2.70/oxygenation index282.00±12.84), thedifferences being statistically significant(P＜0.05). PaO2(53.46±5.63) andoxygenation index(254.57±26.83) of β2agonist group were lower than that ofcontrol group, but the differences being no statistically significant (P＞0.05).(2) The wet/dry weight ratio of the lung tissues showed that the WLLgroup(3.62±0.14) and β2agonist group(3.42±0.10) were significantly higherthan the control group(3.20±0.17), the differ-ence being statistically significant(P＜0.05). But the β2agonist group was lower than WLL group, thedifference being statistically significant(P＜0.05).(3) The general observationof the lung tissue showed that the control group was normal, however edemaand frothy reddish liquid of lung tissues could be found in WLL group and β2agonist group.(4)HE staining showed edematous fluid in the lung-bubblecavities could not be found in the control group, no alveolar damage andmucosal edema. However reddish liquid could be found in the alveolar cavitiesand intersititum of the rabbits from WLL group and the β2agonist group. In themeantime, the alveolar spaces expanded. The pathological score of these threegroups: WLL group(7.2±1.483) and β2agonist group (5.2±1.095) were higherthan control group(0.8±0.837), the difference being statistically significant(P＜0.05).(5) Electron microscopy showed the alveolar epithelial structure of thelung was integrity in the control group, the tight junctions were not damaged,however, in the WLL group and the β2agonist group showed damage of the tightjunctions of the alveolar epithelial.(6) Immunohistochemistry: AQP1proteinwas expressed in the lung tissues of the alveolar epithelium and capillaryendothelial cells around the bronchi and alveoli in the control group. The opticaldensity value of the control group, WLL group and β2agonist group were0.354±0.014,0.504±0.075and0.652±0.041, respectively, there being statistically significant difference among three groups (P＜0.05). Comparedwith WLL group, the OD value of β2agonist group was higher, the differencebeing statistically significant (P＜0.05).(7) Real time fluorescent quantitativePCR: The relative quantity of AQP1mRNA in the WLL group(3.07±0.75) andβ2agonist group(4.74±1.14) were significantly higher than the controlgroup(1.90±1.09), the difference being statistically significant (P＜0.05). Butthe relative quantity of AQP1mRNA in WLL group was lower than that in theβ2agonist group, the difference being statistically significant (P＜0.05).Conclusions:(1) Whole Lung Lavage can cause mild lung injury of rabbit.(2)AQP1expression in the lung tissues of rabbits after WLL is increased.(3) β2agonist could up-regulate the expression of AQP1and alleviate the injury ofalveoli epithelial, which might be one of the mechanisms to promote the residualfluid transport in alveolar cavities resulting from WLL.