title: Endothelin-1 signalling controls early embryonic heart rate in vitro and in vivo.
abstract: OBJECTIVE
  Spontaneous activity of embryonic cardiomyocytes originates from sarcoplasmic reticulum (SR) Ca(2+) release during early cardiogenesis. However, the regulation of heart rate during embryonic development is still not clear. The aim of this study was to determine how endothelin-1 (ET-1) affects the heart rate of embryonic mice, as well as the pathway through which it exerts its effects.
  
  
  METHODS
  The effects of ET-1 and ET-1 receptor inhibition on cardiac contraction were studied using confocal Ca(2+) imaging of isolated mouse embryonic ventricular cardiomyocytes and ultrasonographic examination of embryonic cardiac contractions in utero. In addition, the amount of ET-1 peptide and ET receptor a (ETa) and b (ETb) mRNA levels were measured during different stages of development of the cardiac muscle.
  
  
  RESULTS
  High ET-1 concentration and expression of both ETa and ETb receptors was observed in early cardiac tissue. ET-1 was found to increase the frequency of spontaneous Ca(2+) oscillations in E10.5 embryonic cardiomyocytes in vitro. Non-specific inhibition of ET receptors with tezosentan caused arrhythmia and bradycardia in isolated embryonic cardiomyocytes and in whole embryonic hearts both in vitro (E10.5) and in utero (E12.5). ET-1-mediated stimulation of early heart rate was found to occur via ETb receptors and subsequent inositol trisphosphate receptor activation and increased SR Ca(2+) leak.
  
  
  CONCLUSIONS
  Endothelin-1 is required to maintain a sufficient heart rate, as well as to prevent arrhythmia during early development of the mouse heart. This is achieved through ETb receptor, which stimulates Ca(2+) leak through IP3 receptors.
authors: Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland.
authors: S
authors: S
authors: Karppinen
authors: R
authors: R
authors: Rapila
authors: K
authors: K
authors: Mäkikallio
authors: S L
authors: SL
authors: Hänninen
authors: J
authors: J
authors: Rysä
authors: O
authors: O
authors: Vuolteenaho
authors: P
authors: P
authors: Tavi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015150:Echocardiography, Doppler; D019332:Endothelin-1 / Q000378:metabolism*; D006321:Heart / Q000196:embryology*; D006339:Heart Rate / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D060888:Real-Time Polymerase Chain Reaction; D044023:Receptor, Endothelin B / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D019332:Endothelin-1; D053496:Inositol 1,4,5-Trisphosphate Receptors; D044023:Receptor, Endothelin B; D002118:Calcium
keywords: Ca2+ oscillations; ET‐1; E‐C coupling; IP3; development; heart