title: Isolation and characterization of atrioventricular nodal cells from neonate rabbit heart.
abstract: BACKGROUND
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: Cardiovascular Sciences, Child and Family Research Institute, Vancouver, British Columbia, Canada.
authors: Xiao
authors: X
authors: Ye Sheng
authors: Yang
authors: Y
authors: Qu
authors: Pauline
authors: P
authors: Dan
authors: Eric
authors: E
authors: Lin
authors: Linda
authors: L
authors: Korthout
authors: Aaron
authors: A
authors: Bradford
authors: Leif
authors: L
authors: Hove-Madsen
authors: Shubhayan
authors: S
authors: Sanatani
authors: Glen F
authors: GF
authors: Tibbits
mesh_terms: D000200:Action Potentials; D000818:Animals; D000831:Animals, Newborn; D001283:Atrioventricular Node / Q000166:cytology* / Q000378:metabolism; D001683:Biological Clocks; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002469:Cell Separation; D018031:Connexin 43 / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000378:metabolism; D004553:Electric Conductivity; D017097:Electric Impedance; D007150:Immunohistochemistry; D016900:Neurofilament Proteins / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D013997:Time Factors; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D018031:Connexin 43; D054815:Cyclic Nucleotide-Gated Cation Channels; D016900:Neurofilament Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019831:Sodium-Calcium Exchanger; D000099211:Phospholamban; C061195:neurofilament protein M