Three distinct types of Ca(2+) waves in Langendorff-perfused rat heart revealed by real-time confocal microscopy.
Although Ca(2+) waves in cardiac myocytes are regarded as arrhythmogenic substrates, their properties in the heart in situ are poorly understood. On the hypothesis that Ca(2+) waves in the heart behave diversely and some of them influence the cardiac function, we analyzed their incidence, propagation velocity, and intercellular propagation at the subepicardial myocardium of fluo 3-loaded rat whole hearts using real-time laser scanning confocal microscopy. We classified Ca(2+) waves into 3 types. In intact regions showing homogeneous Ca(2+) transients under sinus rhythm (2 mmol/L [Ca(2+)](o)), Ca(2+) waves did not occur. Under quiescence, the waves occurred sporadically (3.8 waves. min(-1) x cell(-1)), with a velocity of 84 microm/s, a decline half-time (t(1/2)) of 0.16 seconds, and rare intercellular propagation (propagation ratio <0.06) (sporadic wave). In contrast, in presumably Ca(2+)-overloaded regions showing higher fluorescent intensity (113% versus the intact regions), Ca(2+) waves occurred at 28 waves x min(-1) x cell(-1) under quiescence with a higher velocity (116 microm/s), longer decline time (t(1/2) = 0.41 second), and occasional intercellular propagation (propagation ratio = 0.23) (Ca(2+)-overloaded wave). In regions with much higher fluorescent intensity (124% versus the intact region), Ca(2+) waves occurred with a high incidence (133 waves x min(-1) x cell(-1)) and little intercellular propagation (agonal wave). We conclude that the spatiotemporal properties of Ca(2+) waves in the heart are diverse and modulated by the Ca(2+)-loading state. The sporadic waves would not affect cardiac function, but prevalent Ca(2+)-overloaded and agonal waves may induce contractile failure and arrhythmias.
Kaneko
T
T
Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Tanaka
H
H
Oyamada
M
M
Kawata
S
S
Takamatsu
T
T
D000814:Aniline Compounds; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003199:Computer Systems; D004562:Electrocardiography; D005456:Fluorescent Dyes; D006321:Heart / Q000502:physiology; D006339:Heart Rate; D066298:In Vitro Techniques; D018613:Microscopy, Confocal / Q000379:methods*; D009206:Myocardium / Q000378:metabolism*; D009994:Osmolar Concentration; D010477:Perfusion; D051381:Rats; D014966:Xanthenes
D000814:Aniline Compounds; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium