Document Detail


Calcium dynamics and the mechanisms of atrioventricular junctional rhythm.
MedLine Citation:
PMID:  20797495     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVES: The purpose of this study was to test the hypothesis that rhythmic spontaneous sarcoplasmic reticulum calcium (Ca) release (the "Ca clock") plays an important role in atrioventricular junction (AVJ) automaticity.
BACKGROUND: The AVJ is a primary backup pacemaker to the sinoatrial node. The mechanisms of acceleration of AVJ intrinsic rate during sympathetic stimulation are unclear.
METHODS: We simultaneously mapped transmembrane potential and intracellular Ca in Langendorff-perfused canine AVJ preparations that did not contain sinoatrial node (n = 10).
RESULTS: Baseline AVJ rate was 37.5 +/- 4.0 beats/min. The wavefront from leading pacemaker site propagated first through the slow pathway, then the fast pathway and atria. There was no late diastolic Ca elevation (LDCAE) at baseline. Isoproterenol up to 3 micromol/l increased heart rate to 100 +/- 6.8 beats/min, concomitant with the appearance of LDCAE that preceded the phase 0 of action potential by 97.3 +/- 35.2 ms and preceded the onset of late diastolic depolarization by 23.5 +/- 3.5 ms. Caffeine also produced LDCAE and AVJ acceleration. The maximal slope of LDCAE and diastolic depolarization always colocalized with the leading pacemaker sites. Ryanodine markedly slowed the rate of spontaneous AVJ rhythm. Isoproterenol did not induce LDCAE in the presence of ryanodine. The I(f) blocker ZD 7288 did not prevent LDCAE or AVJ acceleration induced by isoproterenol (n = 2).
CONCLUSIONS: Isoproterenol and caffeine induced LDCAE and accelerated intrinsic AVJ rhythm. Consistent colocalization of the maximum LDCAE and the leading pacemaker sites indicates that the Ca clock is important to the intrinsic AVJ rate acceleration during sympathetic stimulation.
Authors:
Daehyeok Kim; Tetsuji Shinohara; Boyoung Joung; Mitsunori Maruyama; Eue-Keun Choi; Young Keun On; Seongwook Han; Michael C Fishbein; Shien-Fong Lin; Peng-Sheng Chen
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of the American College of Cardiology     Volume:  56     ISSN:  1558-3597     ISO Abbreviation:  J. Am. Coll. Cardiol.     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-08-27     Completed Date:  2010-09-17     Revised Date:  2013-06-06    
Medline Journal Info:
Nlm Unique ID:  8301365     Medline TA:  J Am Coll Cardiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  805-12     Citation Subset:  AIM; IM    
Copyright Information:
Copyright (c) 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.
Affiliation:
Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Krannert Institute of Cardiology, Indianapolis, Indiana, USA.
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MeSH Terms
Descriptor/Qualifier:
Adrenergic beta-Agonists / pharmacology
Animals
Atrioventricular Node / drug effects,  physiology*
Caffeine / pharmacology
Calcium / metabolism*
Dogs
Isoproterenol / pharmacology
Ryanodine / pharmacology
Sarcoplasmic Reticulum / metabolism*
Grant Support
ID/Acronym/Agency:
71140//PHS HHS; P01 HL078931-03/HL/NHLBI NIH HHS; P01 HL78931/HL/NHLBI NIH HHS; R01 HL071140/HL/NHLBI NIH HHS; R01 HL071140-08/HL/NHLBI NIH HHS; R01 HL078932-06/HL/NHLBI NIH HHS; R01 HL78932/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Adrenergic beta-Agonists; 15662-33-6/Ryanodine; 58-08-2/Caffeine; 7440-70-2/Calcium; 7683-59-2/Isoproterenol
Comments/Corrections

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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