Protective Effects Of The Calcium Channel Agonist Bay K8644 On The Lungs Against Ischemia-reperfusion Injury In Rabbits

ObjectivesInvestigate the protective effect and mechanism of the preconditioning with calcium channel agonist Bay K8644 of the lungs against ischemia-reperfusion injury in rabbits.MethodsFourty rabbits were divided into four groups randomly: Sham-operated group (Sham, n=10),Ischemic-reperfusion injury group (I/R,n=10), Ischemic preconditioning group(IP,n=10), Bay K8644 preconditioning group (Bay K8644, n=10). Using in vivo model of lung ischemia-reperfusion injury,after test we detected lung W/D changes,lung tissue activities of SOD,lung tissue MPO content,lung tissue MDA content,serum activities of SOD and serum MDA content,also observed morphological changes and ultrastructural changes of lung tissue and expression of SP-A.Results1.The lung W/D changes:After reperfusion,compared with I/R group,the W/D of Sham group,Bay K8644 group and IP group was lower significantly,Sham group,Bay K8644 group,IP group and the I/R group difference was statistically significant (P<0.05);compared with IP group,the Bay K8644 group showed no significant difference on the index(P>0.05).2.Lung tissue SOD activity and MDA,MPO content:Sham group, Bay K8644 group and the IP group of the lung tissue SOD activity was significantly higher than the I/R group,MDA content was lower than the I/R group,MPO content was significantly lower than the I/R group, Sham group,Bay K8644 group,IP group and the I/R group difference was statistically significant (P<0.05);Bay K8644 group and the IP group difference was not statistically significant (P> 0.05).3.Serum SOD activity and MDA content:Within groups:With the experimental observation of prolonged in the Sham group,there was slightly lower in SOD activity and mild increase in MDA content, not statistically significant (P> 0.05).However,the I/R group,Bay K8644 group and IP group with prolongation of reperfusion,SOD activity was significantly decreased,MDA content was increased,compared with before ischemia significantly different (P<0.05).Between groups:SOD activity before ischemia Bay K8644 group compared with Sham group and I/R group decreased slightly,while the MDA content increased slightly,but no significant difference (P> 0.05);Compared with the Sham group,Bay K8644 group,I/R group and the IP group with reperfusion time prolonged,the corresponding time points SOD activity decreased gradually,while the corresponding time points MDA content increased gradually,were statistically significant (P <0.05);Compared with the I/R group,Bay K8644 group and the IP group decreased less SOD activity,MDA content increased level was not high,compared at different time points after ischemia,were significantly different (P<0.05);Compared with IP group,there was no significant difference at different corresponding time points in the serum SOD activity and MDA content (P>0.05).4.Lung tissue under light microscope morphological changes:Sham group:Pulmonary interstitial and alveolar structural integrity, no significant damage,no significant red blood cell leakage.I/R group:Athological lung tissue showed diffuse changes,atelectasis,pulmonary interstitial edema widened,a large number of inflammatory cell infiltration,alveolar wall congestion and edema,thickening,inflammatory cell infiltration,alveolar exudate a large number of red blood cells,capillary congestion and edema,vascular wall thickening,vascular and inflammatory cell infiltration,exudation serious,lung injury significantly.IP group and Bay K8644 group:Two groups were similar to the basic pathology,pulmonary interstitial edema to a lesser extent,less infiltration of inflammatory cells,red blood cells within the alveolar exudate was not obvious,the basic integrity of alveolar structure,damage than the I/R group was significantly reduced.5.Lung tissue under electron microscopy ultrastructural changes: Sham group:Normal alveolar structure.Typeâ…¡alveolar epithelial cell structural integrity,membrane connection close,mitochondria and endoplasmic reticulum and other organelles were normal,large and dense microvilli.Part of the alveolar capillary congestion,capillary endothelial cells had no obvious abnormalities.I/R group:Thickened alveolar septa and edema.Typeâ…¡alveolar epithelial cells lack microvilli,a large number of empty lamellar bodies,epithelial granules demyelination,collagen fibrils,a large number of mitochondria and other organelles vacuolization,nuclear condensation and apoptotic-like changed into.Pulmonary capillary endothelial cell swellied,basement membrane thickened,capillary congestion,atresia,stenosis,inflammatory cell infiltration and large increase in interstitial.IP group and Bay K8644:Structure slightly thickened alveolar septum.I epithelial cells only individual mitochondrial swelled.Typeâ…¡alveolar epithelial cell surface microvilli was rare,lamellar bodies existed,there were epithelial part of the degranulation and some vacuolization of mitochondria.Capillary cavity retention of inflammatory cells,congestion,congestion lighter,occasionally lung tissue inflammatory cell infiltration,mild interstitial edema.6.Immunohistochemistry to detect the expression of SP-A:Immunohistochemical staining of SP-A was positive for brown.The SP-A of Sham group,Bay K8644 and IP group in rabbits lung,mainly in the form of a continuous distribution of membranous surface in the alveolar space,part of the cytoplasm of alveolar epithelial cells can also be seen brown granules.Alveolars of Sham group were basic integrity,however,less alveolar fusion in the Bay K8644 group and IP group.I/R group alveolar membranous rarely seen color,granular staining mostly gathered in the alveolar cavity or deposited in the alveolar surface,severe alveolar fusion.Sham group,IP group,Bay K8644 group of SP-A expression was respectively stronger than I/R group,there was significant difference (P<0.05).Bay K8644 group and the IP group was no significant difference (P> 0.05).ConclusionPreconditioning period for the targeted use of appropriate calcium channel agonist Bay K8644 increased transient calcium influx, which had protective effects on lung ischemia-reperfusion and could simulate the endogenous protective effects of IP in the vivo rabbit I/R injury model.