Expression Of Heart Tissue Connexin 43 And The Intervention Effect Of Propofol Under Hemorrhagic Shock Myocardial Injury In Rabbits

Objective: Hemorrhagic shock is clinically very serious and urgent syndrome,occuring in severe trauma and operative bleeding,it can lead to death if not treated in time.HS is characterized by systemic blood volume reduction,lacking of tissue perfusion,hypoxia and anaerobic metabolism,which result in accumulation of lactic acid,a large amount of oxygen free radicals and metabolic products that aggravate the oxidative stress injury causing organ dysfunction or even failure.Although myocardial cells are equipped with strong tolerance against ischemia/hypoxia damage,severe shock will decrease myocardial systolic function,and cardiac output,so as to further injury of other organs.Propofol is used as a common clinical intravenous anesthetic,it can eliminate oxygen radicals and inhibit apoptosis.Researches have shown that propofol preconditioning has an obviously protective effects on hemorrhagic shock and ischemia-reperfusion myocardial injury.Connexin 43?Cx43?is the major protein composition of myocardial gap junctions,the abnormalities of Cx43's quantity,phosphorylation and spatial distribution can affect the electrical coupling of gap junctions as well as the synchronous myocardial contraction function.Studies have shown that acute myocardial ischemia can induce the redistribution of Cx43,which presents mainly in the changes of protein expression,distribution pattern and phosphorylation.This study intends to evaluate the effects of propofol preconditioning on Cx43 protein expression in rabbit of myocardial injury inducing by hemorrhagic shock,meanwhile provides the references to mechanism of propofol to reduce myocardial injury caused by hemorrhagic shock.Methods: Twenty-four healthy male New Zealand rabbits aged 5⁷ months,weighted 2.5³ kg,provided by the experimental animal center of Hebei Medical University,were randomized into 3 groups?n=8 each?: sham operation group?group S?;hemorrhagic shock group?group HS?and propofol group?group P?.Rabbits were placed in a special cage after weighed,taken an injection of 3% sodium pentobarbital?30mg/kg?along the right ear vein for anesthesia,then the rabbits were fixed on the operating table.Operative regions were conducted with skin preparation,iodophor disinfection and 1% lidocaine infiltration anesthesia,then sheared in the middle of the neck skin,separated the trachea and performed tracheotomy intubation?ID=3.0mm?and retained their spontaneous respiration.The rabbits' right common carotid arteries were separated and stabbed with a 24 G needle,connected with Philips G60 multifunctional monitor for continued blood pressure?BP?and mean arterial pressure?MAP?.The rabbits' bilateral femoral triangles were sheared after 1% lidocaine infiltration anesthesia,seperated and stabbed with a 24G needle into them,connected with a three-way for bleeding,collecting blood samples and blood transfusion and medication.Finally,3mg/kg heparin was administered.Group S was only undergone tracheotomy intubation,the right carotid artery and femoral vein catheterization,no bleeding;Group P was unndergone injection of propofol 5 mg/kg before 10 minutes for bleeding through the right femoral vein and remained the injection by minipump at the speed of 20 mg·kg^-1·h_-1 lasting to the 120 th minutes of shock;Group S and HS were injected intravenously with the same volume of normal saline.The wigger 's modified method was use for bleeding through the left femoral artery so that the MAP could decrease to 40 mmHg within 10 minutes,the amount of bleeding was about 30⁵0% of total blood volume,MAP needed to remain 35⁴5 mmHg through bleeding and reinfusion.Blood samples were collected at the time of bleeding?T₀?,30 min?T₁?,60 min?T₂?,90 min?T₃?and 120 min?T₄?after shock,for the sake of determination the serum cTn I and lactate at each time.The rabbits were undergone mechanical ventilation after T₄ by connecting to HX-200 animal ventilator with the tidal volume of 10¹5 ml/kg,respiratory rate of 30⁴0 times/minute,inspiratory/expiratory of 1:1.5 and oxygen concentration of 100%.They were slivered the chest and taken the apex of heart tissue,divided into two halves,one in EP tube was preservated in-80?refrigerator after frozen in liquid nitrogen for 24 h;the other was fixed in 4% paraformaldehyde solution for detection.cTnI in serum was determined by ELISA;Lactate level was detected by arterial blood gas analyzer;heart tissue fixed in 4% paraformaldehyde solution and paraffin-embedding was stained by HE in order to observe the pathological changes by optical microscope;heart tissue preserved in-80? refrigerator was used to detect the expression of Cx43 by Western blot.Results:1 Compared with the group S,serum cTnI in group HS and P increased;compared with group HS,serum cTnI in group P decreased;compared with T₀,serum cTnI in group HS and P increased with time extended?P<0.05?.2 Compared with the group S,lactate level in group HS and P increased;compared with group HS,lactate level in group P decreased;compared with T₀,lactate level in group HS and P increased with time extended?P<0.05?.3 The myocardial cells and fibers showed a normal morphology in group S;the myocardial cells were swelling and fibers were broken,inflammatory cells infiltrated in intercellular space in group HS;the myocardial cells were roughly normal and injured lightly in group P;myocardial damage scores of group HS and P were higher than group S,while compared with group HS,it was lower in group P?P<0.05?.4 Compared with group S,the expression of Cx43 decreased in group HS and P;compared with group HS,Cx43 expression increased in group P?P<0.05?.Conclusions:1 Animal model of hemorrhagic shock can be made successfully by femoral artery bleeding.2 Hemorrhagic shock can cause myocardial damage and decrease Cx43 expression.3 Propofol can attenuate the myocardial damage induced by hemorrhagic shock through upregulating Cx43 expression.