心房颤动犬心房肌细胞三磷酸肌醇1型和2型受体的分布及表达

The expression of IP_3R1 and IP_3R2 in atrial myocytes during atrial fibrillation in dogs

目的探讨心房颤动(房颤)时犬心房肌细胞三磷酸肌醇1型受体(IP3R1)和三磷酸肌醇2型受体(IP3R2)的表达及分布的改变。方法选择10只杂种犬,分为正常对照组和房颤起搏器组,每组5只。房颤起搏器组用起搏器进行房颤式快速起搏,起搏频率(500±20)次/min,术后观察24周。正常对照组不置入起搏器。24周后取出心脏,用RT-PCR、荧光免疫组织化学和Western blot技术检测犬心房肌细胞IP3R1、IP3R2在mRNA表达水平,蛋白水平的表达和分布。结果房颤起搏器组犬心房肌细胞IP3R1、IP3R2在mRNA和蛋白水平的表达明显高于正常对照组(P<0.05),IP3R1主要在细胞质内表达,IP3R2除了在细胞质内表达增加外,在心房肌细胞闰盘、细胞膜和细胞核膜分布均显著增加。结论房颤时犬心房肌细胞IP3R1和IP3R2的表达上调及功能增强,IP3R2是与心房肌细胞内钙信号调控的主要受体,可能也参与细胞缝隙连接之间的钙信号传递过程。

Objective To investigate the expression of inositol 1, 4, 5-triphosphate receptor （IP3R） type 1 and type 2 in the atrial myocytes during atrial fibrillation. Methods Ten adult mongrel dogs were randomly divided into 2 groups： 5 dogs underwent continuous rapid atrial pacing （500 beats/rain） for twenty-four weeks to create persistent atrial fibrillation, and the other 5 size-matched dogs without pacemaker implantation were used as controls. The dog＇s hearts were taken out and the expression of IPa R1 and IPa R2 in atrial tissue was examined. The distribution of IP3 R1 and IP3R2 was examined by immunofluorescence staining. The mRNA and protein level of IP3R1 and IP3 R2 were measured by reverse transcription-polymerase chain reaction and Western blot. Results In atrial tissue during atrial fibrillation,IP3R1 was found within the cytosol of myocytes, and IP3 R2 protein was found within the cytosol of myocytes, cellular membrane, nuclear membrane, and intercalated discs. The expression of IPa R1 and IPa R2 was increased during atrial fibrillation, and the later expression was more wide. The mRNA and protein level of both IPa R1 and IP3R2 were elevated during atrial fibrillation compared with the normal dogs （P 〈0.05）. Conclusions The expression of IP3R1 and IP3R2 is up-regulated and the function of IP3R is enhanced during atrial fibrillation. IP3 R2 may be more important than IP3 R1 in regulating Ca^2＋ signal in atrial myocytes,and may take part in the Ca^2＋ signal transmission in intercalated discs.