Role Of Connxein43 During Myocardial Apoptosis Induced By Hemorrhagic Shock And Resuscitation In Rabbits

Objective: Acute hemorrhagic shock as a common urgent and serious condition mainly occurs in surgical,et al.Positive and effective management will directly determine patient's prognosis,ischemic and anoxic damage is the key feature of hemorrhagic shock.When blood volume is insufficient decompensated state can lead to multiple organ dysfunction.Myocardial ischemia will result in irreversible organ damages even death.Some scholars regard HS/R as a systemic ischemia-reperfusion injury.Myocardial has stronger tolerance to ischemia-hypoxia,but when massive blood lose sharply the function of heart is reduced,further aggravat ischemic organ hypoperfusion[1].Myocardial gap junction(GJ)is one of the important communication between myocardial cells,mainly composed of gap junction protein 43(Cx43).GJ has realized the electric coupling of cells and chemical information exchange[2].Researches have shown that heptanol preconditioning has an obviously protective effects on hemorrhagic shock and ischemia-reperfusion myocardial injury[3,4].The expression of Cx43 protein,phosphorylation status and distribution and GJ is closely connected with communication function[5].Studies have shown that blood loss before giving advance GJ channel blockers heptanol on ischemic myocardial protection[6].The expression and distribution change of Cx43 in myocardial cell membranes and organelles were involved with the cell division cycle and the regulation of cell death and survival on acute myocardial ischemia,however it is not clear on relationship of Cx43 protein and cell apoptosis.In this study,we built New Zealand white rabbit hemorrhagic shock and resuscitation model,explore the change of connxein43(Cx43)induced by hemorrhagic shock and resuscitation,and analyze the role of connxein43(Cx43)during myocardial apoptosis.Methods: Thirty-two healthy adult New Zealand male rabbits,aged 5~7 months,weighing 2.5~3.0kg,were randomly divided into 4 groups(n=8 each)using a random number table: sham operation group(group S),hemorrhagic shock and resuscitation group(group HSR),heptanol preconditioning group(group HP),heptanol vehicle dimethyl sulfoxide group(group DMSO).Inject 3% sodium pentobarbital 30mg/kg in ear marginal vein for anesthesia.The model of hemorrhagic shock was established by modified Wigger's methods,heptanol 0.6mg/kg was injected in ear marginal vein at 30 min before hemorrhagic shock,while the equal volume of normal saline was given in group HSR and S,and the equal volume of DMSO was given in group DMSO.It was use to bleed through the left femoral artery so that the MAP could decrease to 40 mmHg within 10 minutes,MAP needed to remain 35~45mmHg through bleeding and reinfusion for the 120 min of shock.Then on the back to within 20 to 25 min to lose all blood loss and constant volume physiological saline for recovery,the MAP back to the basic level of 90%,to maintain this level and observation of 60 min.Arterial blood samples were taken before bloodletting at 30 and 60 min of hemorrhagic shock,and at 30 and 60 min of resuscitation.At 60 min after the end of resuscitation,the apex of myocardial tissue were removed,and divided into two halves,half of which fixed in 4% paraformaldehyde solution for detection,and the other half was stored in liquid nitrogen for 24 h and-80? in refrigerator.The cardiac troponin I(c TnI)levels in serum were measured by ELISA.Heart tissue fixed in 4% paraformaldehyde solution and paraffin-embedding was stained by HE in order to observe the pathological changes by optical microscope.The myocardial cell apoptosis was measured by the method of terminal-deoxynucleotidyl transferase mediated d-UTP nick end labeling(TUNEL),the apoptosis index(AI)was calculated and for determination of Cx43 expression by Western blot.Results: 1 Changes of myocardial histopathology Group S rabbit myocardial cells morphology were normal,oval or spindle,and myocardial fibers connected to each other order,and the nuclei were uniform;Myocardial fiber arrangement were irregular,structure disorder and gap widened,the myocardial cells were swollen and hypertrophic and inflammatory cells are infiltrating obviously between myocardial interstitium,can be seen the phenomenon of nuclei are hyperchromatic,pyknosis in HSR and DMSO groups;Compared with HSR group and DMSO group pathological damage degree no difference;HP group cardiomyopathy rational damage,visible rules,the arrangement of myocardial cell myocardial cell mild edema occasional dot necrosis in group HP;2 Changes of the levels of cTnI of rabbits serum Compared with T0,the concentration of serum cTnI was not statistically significant in group S(P>0.05)and was obviously increased in group HSR(P<0.05)at shock 30min(T1),60min(T2)and recovery 30min(T3),60min(T4)point.Compared with group S,the concentration of serum cTnI was obviously increased in HSR,HP and DMSO groups(P<0.05);Compared with group HSR,no significant change was found in the parameters mentioned above in DMSO group(P>0.05),and the concentration of serum cTnI was obviously increased in group HP(P<0.05);3 Expression levels of Cx43 in myocardial tissue Compared with group S,the expression of Cx43 in myocardial tissue down-regulated in HSR,HP and DMSO groups(P<0.05);Compared with group HSR,no significant change was found in the parameters mentioned above in DMSO group(P>0.05),and the expression of Cx43 in myocardial tissue was significantly increased in group HP(P<0.05);4 Changes of myocardial cell apoptosis Compared with group S,A1 was increased in HSR and HP group(P<0.05);Compared with group HSR,no significant change was found in the parameters mentioned above in DMSO group(P>0.05),and AI was decreased in HP group(P<0.05).Conclusion:1 Myocardial Cx43 plays an important role in hemorrhagic shock and resuscitation induced acute myocardial injury rabbits.Raised Cx43 protein expression and improve the level of myocardial cell apoptosis,may be a new target to prevent the HS/R for myocardial injury.2 Heptanol pretreatment relieves oxidative stress during the myocardial injury induced by hemorrhagic shock and resuscitation,its mechanism probably may be inhibited of GJ channel and up-regulation expression of Cx43 in the myocardial tissue.