Real time, confocal imaging of Ca(2+) waves in arterially perfused rat hearts.
OBJECTIVE
The aim of this study was to characterize the spatio-temporal dynamics of slow Ca(2+) waves (SCW's) with cellular resolution in the arterially-perfused rat heart.


METHODS
Wister rat hearts were Langendorff-perfused with Tyrode solution containing bovine-albumine and Dextran. The heart was loaded with the Ca(2+) sensitive dye Fluo-3 AM. Intracellular fluorescence changes reflecting changes in [Ca(2+)](i) were recorded from subepicardial tissue layers using a slit hole confocal microscope with an image intensified video camera system at image rates of up to 50/s.


RESULTS
SCW's appeared spontaneously during cardiac rest or after trains of electrical stimuli. They were initiated preferentially in the center third of the cell and propagated to the cell borders, suggesting a relation between the cell nucleus and wave initiation. They were suppressed by Ca(2+) transients and their probability of occurrence increased with the Ca(2+) resting level. Propagation velocity within myocytes (40 to 180 microm/s) decreased with the resting Ca(2+) level. Intercellular propagation was mostly confined to two or three cells and occurred bi-directionally. Intercellular unidirectional conduction block and facilitation of SCW's was occasionally observed. On average 10 to 20% of cells showed non-synchronized simultaneous SCW's within a given area in the myocardium.


CONCLUSIONS
SCW's occurring at increased levels of [Ca(2+)](i) in normoxic or ischemic conditions are mostly confined to two or three cells in the ventricular myocardium. Spatio-temporal summation of changes in membrane potential caused by individual SCW's may underlie the generation of triggered electrical ectopic impulses.
Baader
Andreas P
AP
University of Bern, Department of Physiology, Bühlplatz 5, 3012 Bern, Switzerland. baader@pyl.unibe.ch
Büchler
Lorenz
L
Bircher-Lehmann
Lilly
L
Kléber
André G
AG
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005456:Fluorescent Dyes; D006329:Heart Conduction System / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D018613:Microscopy, Confocal; D018715:Microscopy, Video; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium