The Effect Of Glucocorticoid In Combined Blast-anoxic Pulmonary Injury In Rats

Backgroud and Aims Lung is one of the major target organs to blast injury.The injury of lung caused by blast injury,which shows as pneumonorrhagia and pneumonedema, is the chief agent resulting in earlier death.Hypoxia may aggravate the injury of lung and cut down further more lung function.The pulmonary surfactant(PS),synthetized and secreted by alveolar epithelial typeâ…¡cells(AT-â…¡) can maintain the normal function of lung.Surfactant-associated proteins(SP) is sine qua non composition of PS,and had general physiological function.SP-A is one of the most important SP.which forming pulmonary surfactant and educing the physiological function of PS.Combined blast-anoxic injury induce the destroy of pulmonary alveoli ultrastructure,and leads to changes of SP-A synthesis and secretion in alveolar epithelial typeâ…¡cells.so,it have important role to improve the condition of patient,which thorough taking effective ways to maintain the level of SP-A and PS in lung.Glucocorticoid have many effects,such as stabilization of lysosomal membrane,decrease the release of enzyme,ROS and inflammatory factor.This study observe injury characteristics of rat(pathomorphologic,lung-body index,pulmonary water containing rate),as well as SP-A in serum and bronchioalveolar lavage fluid(BALF) in combined blast-anoxic injury in rats,and changes of above index after treatment with glucocorticoid,The aim of the study is to understand the mechanisms of blast-anoxic lung injury,and to provide theoretical guide for treatment of combined blast-anoxic injury with glucocorticoid.Methods 112 SD rats were divided into three groups randomly:normal comparative group(NC),combined blast-anoxic injury group(BA),and dexamethasone group(DEX). The rats were inflicted of blast injury by BST-â…¡bio-shock tube.Rats of BA were put into the anoxic-cabin immediately after they were inflicted of blast injury,the anoxic-cabin was then aerated the mixed gas of 12.5%O₂.Rats of DEX were intraperitoneal injection dexamethasone.The concentration of TNF-αand IL-8 in BALF was determined with Elisa.The SP-A content in BALF and serum was determined with Western Blot method. The content of SP-A mRNA in lung tissue was determined with RT-PCT.The pathologic change of the lung tissue,the lung-body index and the pulmonary water containing rate were also observed.Results:1.Characteristics of the injury:in BA group,the main characteristics of the injured rats were dysphoria,tachypnea,cyanosis.The main pathomorphologic characteristics were pulmonary hemorrhage,pneumonedema and inflammatory infiltration.The main characteritics of electron microscope are disruption of alveolar wall,microvilli of alveolar epithelial typeâ…¡cells falling off;decrease of lamellar body.The death peak occurrence at 1 hour after injury.The lung-body index and the pulmonary water containing rate of the injured group were higher than NC,but there were no significant differences between the phases.The mortality of DEX group is less than BA group,the pulmonary water containing rate of DEX group is higher than NC group,but less than BA group.There is no significance of lung-body index between DEX group and BA group.2.The concentration of TNF-αand IL-8 in BALF of BA group were higher than of NC group significantly(P＜0.01).Increase of TNF-αis most significant at 1 hr,and IL-8 shows the same changes at 3 hr.The concentration of TNF-αand IL-8 in BALF of DEX group was less than of NC group,but higher than of BA group significantly(P＜0.01).3.The SP-A level in BALF of BA group was less than of NC group significantly (P＜0.01).There were not statistically significant in different phase(P＞0.05).The SP-A level in BALF of DEX group was less than of NC group,but higher than of BA group significantly(P＜0.01).4.The concentration of SP-A in serum was significantly increasing after injury(BA group vs NC group)(P＜0.01).On the same phase the SP-A level of BA group was higher than NC group.The concentration of SP-A in serum of DEX group was higher than of NC group,but less than of BA group significantly(P＜0.01).There were not statistically significant in different phase of DEX group.5.The SP-A mRNA level in lung of BA group was significantly lower than of the NC group after injury(P＜0.01).The SP-A mRNA level in lung of DEX group was significantly lower than of the NC group after injury(P＜0.01),but it is higher than of NC group (P＜0.01).Conclusion:1.Blast injury and anoxia decrease the level of SP-A significantly,and impact SP-A synthesis of alveolar epithelial typeâ…¡cells severely.2.Inflammatory factor such as TNF-αand IL-8 is the important agent to cause further injuries succeeded with lung injury.Glucocorticoid inhibit the effects of inflammatory factor efficiently.3.Glucocorticoid reduce the SP-A which enter blood through degrade the permeability of blood-gas barrier.It conduct to the restoration of SP-A in lung and extenuation of lung injury.4.Glucocorticoid have direct effects to improve the SP-A synthesis of alveolar epithelial typeâ…¡cells,which is depressed caused by lung injury.Glucocorticoid also inhibit the adverse effects of inflammatory factor to SP-A synthesis.By these,it have very important effects to maintain the level of SP-A in lung and normal lung function.