title: Excitation-contraction coupling of the mouse embryonic cardiomyocyte.
abstract: In the mammalian embryo, the primitive tubular heart starts beating during the first trimester of gestation. These early heartbeats originate from calcium-induced contractions of the developing heart muscle cells. To explain the initiation of this activity, two ideas have been presented. One hypothesis supports the role of spontaneously activated voltage-gated calcium channels, whereas the other emphasizes the role of Ca(2+) release from intracellular stores initiating spontaneous intracellular calcium oscillations. We show with experiments that both of these mechanisms coexist and operate in mouse cardiomyocytes during embryonic days 9-11. Further, we characterize how inositol-3-phosphate receptors regulate the frequency of the sarcoplasmic reticulum calcium oscillations and thus the heartbeats. This study provides a novel view of the regulation of embryonic cardiomyocyte activity, explaining the functional versatility of developing cardiomyocytes and the origin and regulation of the embryonic heartbeat.
authors.affiliation: Institute of Biomedicine, Department of Physiology and Biocenter Oulu, University of Oulu, 90014 Oulu, Finland.
authors.forename: Risto
authors.initials: R
authors.lastname: Rapila
authors.forename: Topi
authors.initials: T
authors.lastname: Korhonen
authors.forename: Pasi
authors.initials: P
authors.lastname: Tavi
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D004622:Embryo, Mammalian / Q000502:physiology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000378:metabolism; D051379:Mice; D009200:Myocardial Contraction / Q000502:physiology*; D032383:Myocytes, Cardiac / Q000502:physiology
chemical_list: D020746:Calcium Channels, L-Type; D053496:Inositol 1,4,5-Trisphosphate Receptors; D002118:Calcium
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