176 449

Cited 19 times in

The role of the calcium and the voltage clocks in sinoatrial node dysfunction

Authors
 Boyoung Joung  ;  Peng-Sheng Chen  ;  Shien-Fong Lin 
Citation
 YONSEI MEDICAL JOURNAL, Vol.52(2) : 211-219, 2011 
Journal Title
YONSEI MEDICAL JOURNAL
ISSN
 0513-5796 
Issue Date
2011
MeSH
Animals ; Arrhythmia, Sinus/physiopathology ; Atrial Fibrillation/physiopathology ; Bradycardia/physiopathology ; Calcium/physiology* ; Calcium Channels/physiology* ; Dogs ; Humans ; Sick Sinus Syndrome/physiopathology ; Sinoatrial Node/physiology ; Sinoatrial Node/physiopathology*
Keywords
Calcium ; sinoatrial node ; sarcoplasmic reticulum ; sick sinus syndrome
Abstract
Recent evidence indicates that the voltage clock (cyclic activation and deactivation of membrane ion channels) and Ca(2+) clocks (rhythmic spontaneous sarcoplasmic reticulum Ca(2+) release) jointly regulate sinoatrial node (SAN) automaticity. However, the relative importance of the voltage clock and Ca(2+) clock for pacemaking was not revealed in sick sinus syndrome. Previously, we mapped the intracellular calcium (Ca(i)) and membrane potentials of the normal intact SAN simultaneously using optical mapping in Langendorff-perfused canine right atrium. We demonstrated that the sinus rate increased and the leading pacemaker shifted to the superior SAN with robust late diastolic Ca(i) elevation (LDCAE) during β-adrenergic stimulation. We also showed that the LDCAE was caused by spontaneous diastolic sarcoplasmic reticulum (SR) Ca(2+) release and was closely related to heart rate changes. In contrast, in pacing induced canine atrial fibrillation and SAN dysfunction models, Ca(2+) clock of SAN was unresponsiveness to β-adrenergic stimulation and caffeine. Ryanodine receptor 2 (RyR2) in SAN was down-regulated. Using the prolonged low dose isoproterenol together with funny current block, we produced a tachybradycardia model. In this model, chronically elevated sympathetic tone results in abnormal pacemaking hierarchy in the right atrium, including suppression of the superior SAN and enhanced pacemaking from ectopic sites. Finally, if the LDCAE was too small to trigger an action potential, then it induced only delayed afterdepolarization (DAD)-like diastolic depolarization (DD). The failure of DAD-like DD to consistently trigger a sinus beat is a novel mechanism of atrial arrhythmogenesis. We conclude that dysfunction of both the Ca(2+) clock and the voltage clock are important in sick sinus syndrome.
Files in This Item:
T201101089.pdf Download
DOI
10.3349/ymj.2011.52.2.211
Appears in Collections:
1. College of Medicine (의과대학) > Dept. of Internal Medicine (내과학교실) > 1. Journal Papers
Yonsei Authors
Joung, Bo Young(정보영) ORCID logo https://orcid.org/0000-0001-9036-7225
URI
https://ir.ymlib.yonsei.ac.kr/handle/22282913/92989
사서에게 알리기
  feedback

qrcode

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Browse

Links