右美托咪定致家兔窦性心动过缓模型中心脏窦房结Cx45和Cx31.9基因表达的变化

Expression changes of cardiac sinus node Cx45,Cx31.9on sinus bradycardia model caused by dexmedetomidine in rabbit

目的观察右美托咪定致家兔窦性心动过缓模型中心脏窦房结中缝隙连接基因蛋白Cx45和Cx31.9表达量的变化,探讨右美托咪定致心脏传导减慢的作用是否与缝隙连接基因蛋白的表达量改变有关。方法成年健康新西兰家兔48只,随机均分为三组,通过耳源静脉注射右美托咪定制备家兔窦性心动过缓模型。戊巴比妥钠基础麻醉后,迅速完成心电图、血压监测的基本操作。C组持续泵注生理盐水,D1组泵入右美托咪定10μg/kg负荷量10min,持续泵注量5μg·kg^(-1)·h^(-1)输入50min,D2组泵入右美托咪定60μg/kg负荷量10min,持续泵注量30μg·kg^(-1)·h^(-1)输入50min,观察结束后迅速开胸取出心脏准确分离心脏窦房结组织,通过免疫组化法检测Cx45、Cx31.9蛋白平均光密度,通过实时荧光定量法检测Cx45、Cx31.9基因相对表达量变化。结果 Cx45基因相对表达量D2组明显多于C、D1组(P<0.05);蛋白平均光密度的改变与之一致;Cx31.9基因相对表达量D1组比C组显著增加(P<0.05),D2组与C组、D1组与D2组差异无统计学意义,蛋白平均光密度的改变与之一致。结论右美托咪定使家兔窦房结低导电性缝隙连接基因蛋白Cx45、Cx31.9的表达增加,缝隙连接基因蛋白表达的变化是导致窦房结区的传导速度减慢原因之一。

Objective To investigate the changes of cardiac sinus node connexin 45（Cx45）,connexin 31.9（Cx31.9）of gap junction in rabbits＇ sinus bradycardia model caused by dexmedetomidine,and to discuss whether the negative frequency and negative conduction caused by Dexmedetomidine are related to the expression changes of connexin.Methods Forty-eight healthy adult New Zealand rabbits were divided into three groups（n=16）.Sinus bradycardia rabbits were prepared by intravenous injecting Dexmedetomidine through ear vein.After rabbits were anesthetized by sodium pentobarbital,basic procedures were quickly completed in order to monitor MAP and ECG.Rabbits in group C were injected with normal saline.Rabbits in group D1 were injected a loading dose of dexmedetomidine 10μg/kg for 10 min,and then continuously pumped 5μg·kg^-1·h^-1 for 50 min.Rabbits in group D2 were pumped a loading dose of dexmedetomidine 60μg/kg for 10 min,and then continuously pumped 30μg·kg^-1·h^-1 for 50 min.After observation hearts were quickly removed and sinus node tissue was dissected.The average optical density of sinus node Cx45,Cx31.9were detected by immunohistochemistry,and the genes expression were detected by real-time quantitative.Results Cx45 gene expression of group D2 showed remarkable increase than groups C and D1（P0.05）,there were no significant differences between groups D1 and C,Cx45 average optical density change were consistent with the gene expression.Cx31.9gene expression of group D1 showed a more remarkable increase than group C（P0.05）,there were no significant differences between groups D2 and C,D1 and D2,Cx31.9average optical density changes were consistent with the gene expression.Conclusion Dexmedetomidine increases the expression of low electrical conductivity Cx45,Cx31.9of gap junction on rabbits＇ sinus node,which is one of the possibly reasons that slow down cardiac conduction velocity in sinus node.