Spatio-temporal changes of intracellular ca2+ during electrically
-evoked contractions in atrial and ventricular cells.
Berlin, Joshua R.
Bockus Research Institute, Graduate Hospital, 415 S. 19th St.,
Philadelphia, PA 19146
APStracts 2:0215H, 1995.
Spatial and temporal changes of intracellular calcium ion
concentration ([Ca2+]i) during stimulated contractions were observed
by confocal microscopy in rat ventricular and guinea pig atrial
myocytes. Fluorescence intensity profiles in fluo-3 AM loaded cells
were collected either from the entire cell, selected regions of the
cell and along a single scanned line across the cell. In rat
ventricular myocytes, the increase of [Ca2+]i following a single
stimulus from field electrodes occurred synchronously across the cell
whether fluo-3 fluorescence was monitored in a narrow longitudinal
region aligned with or along a single z-line oriented perpendicular
to the long axis of the cell. However, during the onset of Ca channel
blockade by nifedipine (5 M), electrical stimulation produced
spatially non-uniform, focal increases of [Ca2+]i. In guinea pig
atrial myocytes, stimulated increases of [Ca2+]i first appeared in
focal regions at the cell periphery before spreading to the cell
interior. Line-scan images showed that the peripheral rise of [Ca2+]i
led that at the center of the cell by 34 + 4 ms (Mean + S.E.M., n =
3). These data demonstrate that the T-tubular network insures
synchronous increases of [Ca2+]i throughout the cell during an action
potential. In the absence of T-tubules or when the number of
sarcolemmal Ca channels opened by membrane depolarization is greatly
reduced, stimulated increases of [Ca2+]i can be observed to arise in
focal regions of the cell.
Received 9 November 1994; accepted in final form 5 May 1995.
APS Manuscript Number H998-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 May 1995.