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目的:窦房结(SAN)是心脏传导系统的重要组成部分,是哺乳动物心脏正常节律的起搏点、心脏自律活动的发源地,正常的SAN功能是心脏泵功能得以实现的前提条件。不同种属动物的SAN尽管在功能方面非常相似,但在位置、形态、组织结构、细胞数目等方面存在诸多的差异。大鼠是最常用的实验动物之一,其SAN体积微小,仅凭肉眼观察难以发现,实验中SAN组织取材存在一定困难。该研究目的是保证SAN光镜和电镜组织取材的准确性,客观观察其组织结构和超微结构。方法:(1)大鼠SAN定位及组织结构观察:采用二级Wistar成年大鼠20只,对右心房及与之相连的近段上腔静脉做水平连续切片,对切片行HE、Masson染色,光镜下观察连续切片,定位SAN并观察组织结构。(2)大鼠SAN超微结构观察:采用二级雄性Wistar成年大鼠10只,依据SAN位置、组织结构特点分两步取材,经树脂定向包埋,半薄切片甲苯胺蓝预染,光镜下定位后,再行超薄切片,透射电镜观察SAN超微结构。结果:(1)正常成年大鼠SAN位置和组织学特点:正常成年大鼠SAN位于上腔静脉与右心耳交界区及其以上的上腔静脉壁内,呈马蹄形/C形;大鼠SAN组织结构疏松,主要含有P细胞、T细胞和少量心房肌细胞,间质胶原纤维含量丰富。(2)正常成年大鼠SAN超微结构特点:甲苯胺蓝预染半薄切片的方法简便迅速,着色效果好,可有效缩短定位时间。电镜观察显示,大鼠SAN内主要含有两种细胞。1P细胞:胞体小,胞浆丰富,细胞器和肌原纤维含量少,几乎不含肌节;2T细胞:胞体较P细胞大,细胞器含量较多,肌原纤维可见明显肌节。结论:成年大鼠SAN取材时一定要保留上腔静脉近心段;大鼠SAN电镜标本要注意取材的位置和包埋的方向,两步法前固定取材有助于大鼠SAN电镜标本的制作;大鼠SAN内细胞的超微结构特点与人及其它哺乳类动物比较一致。
OBJECTIVE: SAN is an important part of cardiac conduction system. It is the pacemaker of cardiac rhythms in mammals and the birthplace of cardiac autonomic activity. The normal SAN function is the precondition of cardiac pump function. SANs of different species, although very similar in function, have many differences in location, morphology, organization and number of cells. Rat is one of the most commonly used experimental animals, its SAN volume is tiny, difficult to find by naked eye observation, there is some difficulty in the experiment of SAN tissue drawing. The purpose of this study is to ensure the accuracy of SAN light microscopy and electron microscopy, to objectively observe its structure and ultrastructure. Methods: (1) SAN localization and histological observation: Twenty adult Wistar rats were used to make horizontal and vertical sections of the right atrium and its adjacent superior vena cava. The sections were stained with HE and Masson, Serial sections were observed under light microscope to locate the SAN and observe the tissue structure. (2) Observation of ultrastructure of SAN in rats: Ten male Wistar male rats were used in two steps according to the location of SAN and the histological structure. The tissue was embedded in resin and pre-dyed with Toluidine blue Microscopically, ultrathin sections were taken and the ultrastructure of SAN was observed by transmission electron microscope. Results: (1) SAN location and histological features of normal adult rats: The normal adult rat SAN was located in the superior vena cava wall at the junction of the superior vena cava and the right atrial appendage with a horseshoe shape / C shape. The rat SAN tissue Loose structure, mainly contains P cells, T cells and a small amount of atrial myocytes, interstitial collagen content. (2) Normal ultrastructure of adult rat SAN ultrastructure: Toluidine blue pre-stained semi-thin sections of the method is simple and rapid, good coloring, which can effectively shorten the positioning time. Electron microscopy showed that there were mainly two kinds of cells in the rat SAN. 1P cells: small cytoplasm, abundant cytoplasm, less organelles and myofibrils content, almost no sarcomere; 2T cells: cell body P cells larger, more organelles, visible myometrial sarcomere. Conclusion: The superior vena cava should be preserved in the adult rat SAN. The location and the direction of embedding should be paid attention to by the SAN electron microscopy in rats. The ultrastructural characteristics of the cells in the rat SAN are consistent with those in humans and other mammals.