Dobutamine Impact On The Expression Of AQP-5、AQP-1、cAMP Level And Alveolar Fluid Clearance In Acute Hyperoxia-induced Lung Injury In Neonatal Rats

Objective:1. To establish a model of acute hyperoxia-induced lung injury in neonatal rats;2. To observe the histopathological effect in lung, brain and kidney of acutehyperoxia-induced injury as well as its affecting the expression of AQP-1,5by comparingwith a control group, and to study the role of AQP-1,5in hyperoxia-induced lung injury;3. To discuss whether that β-adrenalinal receptor agonist, dobutamine, has aprotective effect to hyperoxia-induced injury and affects the expression of AQP-1,5andcAMP by treating with it, and to provide evident of clinical treatments ofhyperoxia-induced injury.Method:72SD rat, all of which were less than3days after birth, were divided into3groupsrandomly: Group Ⅰ,air control group; Group Ⅱ, treated with hyperoxygen and normalsaline (hyperoxia group); Group Ⅲ, treated with hyperoxygen and dobutamine (interferinggroup). Each group had24rats and was subdiveded into2groups by timing of3and7days. Again, each subgroup was divided into2groups by lavaging and non-lavaging.Group Ⅱ and Ⅲ were both incubating in special oxygen boxes with a stableoxygenconcentration of90%-95%. Group Ⅰ was incubating in normal air. Group Ⅲwas injectedof dobutamine (15mg/kg) everyday at the same timepoint from the beginning of thisstudy.The6lavaging groups were performed bronchoalveolar lavage at their differenttimepoints, and to measure the lung permeability index (LPI) and protein level in bothlavaging fluid and serum. The non-lavaging group were executed at timepoints. The leftlungs were weighed and afterwise dried, by which calculating the wet/dry porpotion. Theright upper lungs, part of the brains and kidnyes were HE to observe the pathological changes.Using Westen-blotting to measure the level of AQP-1,5in the remaining of lungs,brains and kidneys, and to measure. Using ELISA to test the variation of cAMP level.Result:1. The general condition: Group Ⅰ(air group) was viable and fed well. GroupⅡ(hyperoxia group) was dull and less active, even dyspnea after hyperoygen abortion. Thesituation of group Ⅲ (interfering group) was between the former two.2. Lung histopathology：in Group Ⅰ(air group), the size, shape and distrubution ofalveoli were even. No congestion and inflamation can be found. In Group Ⅱ(hyperoxiagroup), some capillaries can be found light microscopically dilated and congested after3days of hyper oxygen, and some erythrocytes, inflammatory cells and fluid can be foundexudated. After7days of hyperoxygen, the numbers of alveoli reduced evidently, size gotlargerer, and the gap got wider. The structure of lung tissue were arranged disordered, withan obvious congestion and inflammatory cells exudated. Pink fluid can be seen in alveolarspace. In Group Ⅲ(interfering group), the congestion and inflammation were milder, thegaps were narrower comparing with group Ⅱ.3. The wet/dry porpotion (W/D) of lung tissue: in day3of this study, the W/D ishigher in group Ⅱ than group Ⅰ. And in day7, it is more significantly higher. Besides, theW/D is obviously reduced in both day3and7in group Ⅲ, comparing with group Ⅱ.4. The level of the protein in bronchoalveolar lavage fluid (BLAF): in both day3and7, the BLAF protein level in group Ⅱ is higher than group Ⅰ, and it is follow a timedependence mannar as the exposure time prolonged. However, the protein in group Ⅲisgreatly decreased compared with group Ⅱ.5. the lung permeability index (LPI): the LPI in group Ⅱ is higher than group Ⅰinday3, and it is even more higher in day7. But in group Ⅲ, the LPI is both lower in bothday3and day7than group Ⅱ.6. The expression of AQP-1,5and the variation of cAMP: the Westen-blotting showsthat in group Ⅰ, the AQP-1,5of neonatal rat lung tissue performs a high expression, andthe expression in day7is higher. In group Ⅱ, the AQP-1,5expression was lowere thangroup Ⅰ, and also performed a significant decreasing (p<0.05) as time extented. In groupⅢ, the expression of AQP-1,5was statistically higher(p<0.05) than group Ⅱ in day3andespecially in day7. 7. The histopathology and the variation of the expression of AQP-1and AQP-5inbrain: in group Ⅱ, it is mainly characteristiced by encephaledema, thickened cerebralcortex and neuronal degeneration. However, these changes cannot be found in group Ⅰ.The AQP-5is highly expressed in group Ⅰ and peaked in day7. The AQP-5expression ingroup Ⅱ is creased, especially in day7. The difference of the expression between groupⅠand Ⅱ is significant (p<0.05). However, there is no significant difference between groupⅢ and Ⅱ (p>0.05). There is no AQP-1expression found in any of the three groups.8. The histopathology and the variation of the expression of AQP-1and AQP-5inkidney: in group Ⅱ, it is mainly characteristiced by glomerular capillaries congestion,mesangium hyperplasia, renal cells swelling, interstitial proliferation and a few ofinflammatory cells infiltration. the injury got even more severe as the time of exposureprolonged. However, these changes cannot be found in group Ⅰ. The AQP-1is highlyexpressed in group Ⅰ and the expression in day7is lower than day3. The AQP-1expression in group Ⅱis decreased, especially in day7. The difference of the expressionbetween group Ⅰ and Ⅱ is significant (p<0.05). However, there is no significantdifference between group Ⅲ and Ⅱ (p>0.05). There is no AQP-5expression found in anyof the three groups.Conclusion:1. The chonic hyperoxygen treatment will cause acute multiple organ damage in rats.After HE, the light microscopy shows that in lung tissure, localized congestion andbleeding, inflammatory exudation, the alveoli decreased and structure disordered. As wellas encephaledema, thickened cerebral cortex and neuronal degeneration in brain andglomerular capillaries congestion, mesangium hyperplasia, renal cells swelling, interstitialproliferation and inflammatory cells infiltration in kidney.2. In the model of acute hyperoxia-induced lung injury in neonatal rats, theexpression of AQP-1and AQP-5is decreased and as the extension of oxygen time thedecreasing got more obvious. Besides, the AQP-5expressed higher as the injury of braingetting worth, and AQP-1decreased in kidney. These findings suggest that AQP plays animportant role in the mechanism of hyperoxia-induced multiple organ damage.3. Dobutamine may promote the expression of AQP-1and AQP-5by enhancing theexpression of cAMP, and afterwise alleviate the inflammation and pulmonary edema andperformed a protective effect to hyperoxia-induced lung injury. But more data and reseach is still required for clinical application.