In situ visualization of spontaneous calcium waves within perfused
whole rat heart by confocal imaging.
Minamikawa, Tetsuhiro, Stephen H. Cody, and David A. Williams.
Muscle and Cell Physiology Laboratory, Department of Physiology,
The University of Melbourne, Parkville, Victoria 3052, Australia
APStracts 3:0329H, 1996.
We describe the first direct visualization of [Ca2+]i oscillations in
the perfused whole rat heart. Dye loading at low temperature and
enhanced optical section techniques of confocal microscopy
eliminating refractive index mismatch with use of saline-immersible
objective lens enabled us to image multiple [Ca2+]i waves in the
subepicardial myocardium of the fluo-3-loaded heart. These [Ca2+]i
waves were sporadically seen even with a physiological [Ca2+]o
perfusion, either in a paced or an arrested heart, and propagated
beyond cellular boundaries within the 3-D structures of cardiac
muscle. Under these conditions, the velocity of wave propagation was
60-100 [mu]m/s and the frequency of initiation was relatively low
(< 2 Hz). With an increase in [Ca2+]o, however, the waves became
more prevalent, tended to be multifocal, and an increasing fraction
of waves exhibited faster propagation velocities and higher
frequencies. These results suggest that perfused rat hearts exhibit
spontaneous [Ca2+]i waves in an apparently resting state, and that
under Ca2+ overload conditions the multifocal and high-frequency
waves become more widespread in the heart syncytium, which may
provide understanding of the ionic basis for the summation of
afterdepolarizations and triggering of arrhythmias seen under
pathological conditions.
Received 28 March 1996; accepted in final form 19 July 1996.
APS Manuscript Number H286-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996