title: Angiotensin II does not acutely regulate conduction velocity in rat atrial tissue.
abstract: OBJECTIVE
  Atrial angiotensin II (Ang II) levels are increased in atrial fibrillation and are believed to be important in the pathogenesis of atrial arrhythmias. Ang II reduces intercellular coupling by inhibiting gap junctions (connexins) and may thereby increase the risk of reentry arrhythmia. The aim of the current study was to investigate the acute effect of Ang II on conduction velocity (CV) in atrial tissue from normal and chronically infarcted rats.
  
  
  METHODS
  Contractile force was measured and CV was determined from the conduction time between electrodes placed on the tissue preparation. Expression of AT1a and AT1b receptors was examined by real-time PCR.
  
  
  RESULTS
  Acute stimulation with Ang II did not affect CV in tissue from auricle or atrial free wall. A transient 6.5 ± 3.6% increase in resting tension was observed in atrial free wall preparations, indicating that receptors are present and functional in the free wall preparation. The difference between free wall and auricle was probably not caused by differences in receptor expression since equal amounts of AT1 mRNA were present. To test if myocardial infarction (MI) sensitizes the atrium to Ang II, free atrial wall from rats subjected to 4-5 weeks ventricular MI was examined. Although CV was significantly reduced by MI, no effect on CV of Ang II was seen.
  
  
  CONCLUSIONS
  Ang II does not acutely regulate CV in tissue preparations from the free wall of the left atria or the left auricle. Although ventricular MI reduces CV, this does not sensitize the atria to Ang II.
authors: The Danish National Research Foundation Centre for Cardiac Arrhythmia and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors: Kristine B
authors: KB
authors: Olsen
authors: Thomas H
authors: TH
authors: Braunstein
authors: Charlotte M
authors: CM
authors: Sørensen
authors: Lene N
authors: LN
authors: Axelsen
authors: Niels-Henrik
authors: NH
authors: Holstein-Rathlou
authors: Morten S
authors: MS
authors: Nielsen
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D056988:Anterior Wall Myocardial Infarction / Q000209:etiology / Q000503:physiopathology; D003971:Diastole / Q000187:drug effects*; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D006352:Heart Ventricles / Q000473:pathology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D044140:Receptor, Angiotensin, Type 1; D014662:Vasoconstrictor Agents; D000804:Angiotensin II