Kwong K F, Schuessler R B, Green K G, Laing J G, Beyer E C, Boineau J P, Saffitz J E
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Circ Res. 1998 Mar 23;82(5):604-12. doi: 10.1161/01.res.82.5.604.
Electrical coupling of pacemaker cells at gap junctions appears to play an important role in sinus node function. Although the major cardiac gap junction protein, connexin43 (Cx43), is expressed abundantly in atrial and ventricular muscle, its expression in the sinus node has been a subject of controversy. The objectives of the present study were to determine whether Cx43 is expressed by sinus node myocytes, to characterize the spectrum of connexin expression phenotypes in sinus node pacemaker cells, and to define the spatial distribution of different connexin phenotypes in the intact sinus node. To fulfill these objectives, we performed high-resolution immunohistochemical analysis of disaggregated adult canine sinus node preparations. Using enhanced tissue preservation and antigen retrieval techniques, we also performed immunohistochemical studies on sections of intact canine sinus node tissue. Analysis of disaggregated sinus node preparations revealed three populations of pacemaker cells distinguished on the basis of connexin immunohistochemical phenotype: approximately 55% of cells expressed only connexin40 (Cx40); 30% to 35% of cells expressed Cx43, connexin45 (Cx45), and Cx40; and the remaining cells had no detectable connexin expression. In immunostained sections of intact sinus node, Cx43- and Cx45-positive cells were limited in their distribution and were observed in discrete bundles that appeared to abut atrial myocytes. In contrast, Cx40 immunoreactive signal was widely distributed in the sinus node region. These results indicate that subsets of pacemaker cells express distinct connexin phenotypes. Differential expression of connexins could create regions within the sinus node with different conduction properties, thereby contributing to the nonuniform conduction properties seen in this tissue.
缝隙连接处起搏细胞的电偶联似乎在窦房结功能中起重要作用。尽管主要的心脏缝隙连接蛋白连接蛋白43（Cx43）在心房和心室肌中大量表达，但其在窦房结中的表达一直存在争议。本研究的目的是确定Cx43是否由窦房结心肌细胞表达，表征窦房结起搏细胞中连接蛋白表达表型的谱，以及确定完整窦房结中不同连接蛋白表型的空间分布。为实现这些目标，我们对成年犬窦房结分离标本进行了高分辨率免疫组织化学分析。使用增强的组织保存和抗原修复技术，我们还对完整犬窦房结组织切片进行了免疫组织化学研究。对分离的窦房结标本的分析揭示了基于连接蛋白免疫组织化学表型区分的三种起搏细胞群体：约55%的细胞仅表达连接蛋白40（Cx40）；30%至35%的细胞表达Cx43、连接蛋白45（Cx45）和Cx40；其余细胞未检测到连接蛋白表达。在完整窦房结的免疫染色切片中，Cx43和Cx45阳性细胞分布受限，在似乎邻接心房肌细胞的离散束中观察到。相比之下，Cx40免疫反应信号在窦房结区域广泛分布。这些结果表明起搏细胞亚群表达不同的连接蛋白表型。连接蛋白的差异表达可在窦房结内形成具有不同传导特性的区域，从而导致该组织中出现的不均匀传导特性。
