Cardiovascular Sciences, Child and Family Research Institute, Vancouver, British Columbia, Canada.
Circ Arrhythm Electrophysiol. 2011 Dec;4(6):936-46. doi: 10.1161/CIRCEP.111.964056. Epub 2011 Oct 14.
The properties of the atrioventricular (AV) node in the neonate heart and its role in unique pediatric cardiac arrhythmias such as junctional ectopic tachycardia (JET) are poorly understood. This is due in large part to the dearth of information on the structure and physiology of the AV node in the immature myocardium.
Sinoatrial nodal cells (SANCs), AV nodal tissues, and myocytes (AVNCs) were obtained from neonatal (10-day-old) rabbits, and the histological, immunohistological, and electrophysiological properties were characterized in detail. Masson's trichrome histological staining clearly delineated AV nodal structures including the inferior nodal extension, compact node, and the bundle of His region. AV tissue sections and AVNCs were immunolabeled against neurofilament 160 (NF160), connexin 43 (Cx43), hyperpolarization-activated, cyclic nucleotide modulated channel (HCN4), sodium/calcium exchanger, ryanodine receptor, sarcoplasmic/endoplasmic reticulum Ca(2+) pump (SERCA), and phospholamban (PLB). In AVNCs with triple-positive NF160, SERCA, and PLB labeling, SERCA and PLB were found with high degrees of colocalization. The majority (59%) of NF160-positive AVNCs were found to coexpress HCN4. NF160 and HCN4 expression was found to be even higher in SANCs, where 88% of SANCs exhibited coexpression. Spontaneous action potentials recorded from isolated neonatal AVNCs were uniformly of the atrionodal type, showing none of the action potential heterogeneities found in the mature heart. Current recordings found the hyperpolarization-activated funny current (I(f)) in 55% (11 of 21 cells) of AVNCs, consistent with the immunocytochemistry results.
This represents the first detailed electrophysiological and immunohistological report of the neonatal AV node and lays the groundwork for a better understanding of heart rate regulation and unique arrhythmias in the neonate heart.
新生儿心脏的房室（AV）结的特性及其在结性异位心动过速（JET）等独特儿科心律失常中的作用知之甚少。这在很大程度上是由于关于未成熟心肌中 AV 结的结构和生理学的信息匮乏。
从新生（10 天大）兔中获得窦房结细胞（SANCs）、房室结组织和心肌细胞（AVNCs），并详细描述其组织学、免疫组织化学和电生理特性。Masson 三色组织学染色清楚地区分了房室结结构，包括下结延伸、致密结和希氏束区域。AV 组织切片和 AVNCs 被针对神经丝 160（NF160）、连接蛋白 43（Cx43）、超极化激活、环核苷酸调制通道（HCN4）、钠/钙交换器、兰尼碱受体、肌浆/内质网 Ca2+泵（SERCA）和磷酸化肌球蛋白结合蛋白（PLB）进行免疫标记。在具有三重阳性 NF160、SERCA 和 PLB 标记的 AVNCs 中，发现 SERCA 和 PLB 具有高度的共定位。发现大多数（59%）NF160 阳性 AVNCs 共表达 HCN4。在 SANCs 中发现 NF160 和 HCN4 的表达更高，其中 88%的 SANCs 表现出共表达。从分离的新生 AVNC 记录的自发动作电位均为典型的房室结型，没有成熟心脏中发现的动作电位异质性。电流记录发现 55%（21 个细胞中的 11 个）的 AVNCs 中存在超极化激活有趣电流（I(f))，与免疫细胞化学结果一致。
这是对新生 AV 结的首次详细电生理和免疫组织化学报告，为更好地理解新生儿心脏的心率调节和独特心律失常奠定了基础。
