Functional and morphological evidence for a ventricular conduction system in zebrafish and Xenopus hearts
Functional and morphological evidence for a ventricular conduction system in zebrafish and Xenopus hearts
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DOI：
10.1152/ajpheart.00870.2002
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发表时间：
2003-04-01
影响因子：
4.8
通讯作者：
Thompson, RP
中科院分区：
文献类型：
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作者：
Sedmera, D;Reckova, M;Thompson, RP
斑马鱼和爪蟾已经成为研究脊椎动物许多器官系统（包括心脏）发育的流行模式生物。然而，目前尚不清楚这些物种的单心室心脏是否具有高等脊椎动物中发现的特殊心室传导系统的等效物。用电压敏感染料对成年斑马鱼（Danio rerio）和非洲蟾蜍（Yenopus laevis）的离体心脏进行染色，并以自发和有节奏的节奏进行光学定位，随后进行组织学检查，重点观察心房和心室之间的心肌连续性。斑马鱼和蟾爪的平均激活时间分别为20 +/- 2 ms和50 +/- 2 ms，激发波通过心房的传播均匀。延迟47 +/- 8和414 +/- 16 ms后，脑室首先在脑尖区激活。异位心室激活的传播速度明显更慢（总心室激活时间：斑马鱼为24 +/- 3 vs. 14 +/- 2 ms，非洲爪鱼为74 +/- 14 vs. 35 +/- 9 ms）。虽然我们没有观察到脑室内任何组织学上明确的特化传导细胞束，但有明显的多唾液酸-神经细胞粘附分子染色的小梁带，在房室管和脑室尖端之间形成直接的心肌连续性；也就是心外膜突破的位置。因此，我们得出结论，这些心脏能够实现在明显缺乏分化传导束的高等脊椎动物中观察到的顶点到基部的心室激活模式，这表明心室小梁在功能上相当于他-浦肯野系统。
Zebrafish and Xenopus have become popular model organisms for studying vertebrate development of many organ systems, including the heart. However, it is not clear whether the single ventricular hearts of these species possess any equivalent of the specialized ventricular conduction system found in higher vertebrates. Isolated hearts of adult zebrafish (Danio rerio) and African toads (,Yenopus laevis) were stained with voltage-sensitive dye and optically mapped in spontaneous and paced rhythms followed by histological examination focusing on myocardial continuity between the atrium and the ventricle. Spread of the excitation wave through the atria was uniform with average activation times of 20 +/- 2 and 50 +/- 2 ms for zebrafish and Xenopus toads, respectively. After a delay of 47 +/- 8 and 414 +/- 16 ms, the ventricle became activated first in the apical region. Ectopic ventricular activation was propagated significantly more slowly (total ventricular activation times: 24 +/- 3 vs. 14 +/- 2 ms in zebrafish and 74 +/- 14 vs. 35 +/- 9 ms in Xenopus). Although we did not observe any histologically defined tracts of specialized conduction cells within the ventricle, there were trabecular bands with prominent polysialic acid-neural cell adhesion molecule staining forming direct myocardial continuity between the atrioventricular canal and the apex of the ventricle; i.e., the site of the epicardial breakthrough. We thus conclude that these hearts are able to achieve the apex-to-base ventricular activation pattern observed in higher vertebrates in the apparent absence of differentiated conduction fascicles, suggesting that the ventricular trabeculae serve as a functional equivalent of the His-Purkinje system.