title: Excitation-dependent intracellular Ca2+ waves at the border zone of the cryo-injured rat heart revealed by real-time confocal microscopy.
abstract: Intracellular Ca2+ waves, which develop under Ca2+-overloaded conditions of the injured myocardium, are regarded as an important substrate for triggered arrhythmias. However, little is known about whether Ca2+ waves arise or become proarrhythmic in the injured heart in situ. On the hypothesis that injured myocardium manifests frequent Ca2+ waves and produce an oscillatory [Ca2+]i rise leading to triggered activity, we applied cryo-injury to the epicardial surface of fluo 3-AM-loaded perfused rat hearts and analyzed spatiotemporal [Ca2+]i changes at border zones of the injured myocardium using real-time confocal microscopy. In intact regions Ca2+ waves barely emerged, whereas the border zone myocardium exhibited frequent Ca2+ waves, propagating randomly within the individual cells. Two different types of Ca2+ waves were identified: highly frequent waves (159.6+/-86.5 waves/min/cell, n=266) adjacent to the cryo-ablated regions, and less frequent waves (79.0+/-50.1 waves/min/cell, n=160) slightly farther (>2 cells) away from the ablated regions (vicinities). The former Ca2+ waves emerged asynchronously to Ca2+ transients. Contrariwise, the latter depended on ventricular excitation: they vanished instantaneously on Ca2+ transients, but emerged more frequently and propagated more swiftly after cessation of higher-frequency pacing. Immediately after 3-Hz pacing, some cryo-injured hearts exhibited oscillatory [Ca2+]i rises; an instantaneous and synchronous elevation of [Ca2+]i followed by burst occurrence of Ca2+ waves with a gradual decrease in incidence and propagation velocity in a considerable number of cells. These observations indicate that myocardial injury induces Ca2+ waves in the heart, and that their synchronous occurrence could become a substrate for triggered arrhythmias.
authors.affiliation: Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Kyoto, 602-0841, Japan. ttakam@basic.kpu-m.ac.jp
authors.forename: Hideo
authors.initials: H
authors.lastname: Tanaka
authors.forename: Masahito
authors.initials: M
authors.lastname: Oyamada
authors.forename: Eiji
authors.initials: E
authors.lastname: Tsujii
authors.forename: Takuya
authors.initials: T
authors.lastname: Nakajo
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Takamatsu
mesh_terms: D000814:Aniline Compounds / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D003080:Cold Temperature / Q000009:adverse effects*; D003199:Computer Systems; D003600:Cytosol / Q000378:metabolism; D005456:Fluorescent Dyes / Q000032:analysis; D006335:Heart Injuries / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D017136:Ion Transport; D008297:Male; D018613:Microscopy, Confocal; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D014966:Xanthenes / Q000032:analysis
chemical_list: D000814:Aniline Compounds; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium