AJP - Heart and Circulatory Physiology, Vol 257, Issue 2 665-H673, Copyright © 1989 by American Physiological Society
Laser backscatter studies of intracellular Ca2+ oscillations in isolated hearts
M. D. Stern, H. F. Weisman, D. G. Renlund, G. Gerstenblith, O. Hano, P. S. Blank and E. G. Lakatta
Laboratory of Cardiovascular Science, National Institute on Aging, Baltimore 21224.
We measured intensity fluctuations of 633 nm laser light backscattered from
the epicardial surface of isolated, perfused rat and rabbit hearts.
Scattered light intensity fluctuations (SLIF) were detected from
verapamil-arrested rat hearts. The frequency of SLIF was increased by
maneuvers that raise intracellular calcium. SLIF were abolished by removal
of extracellular calcium with ethylene glycol-bis(beta-aminoethyl
ether)-N,N,N',N'-tetraacetic acid and by blockade of sarcoplasmic reticulum
calcium release by ryanodine. SLIF were not accompanied by any surface
electro-cardiogram and were not abolished by 144 mM extracellular
potassium. SLIF were absent in rabbit hearts under base-line conditions but
could be provoked by calcium loading using zero potassium and ouabain. We
conclude that backscatter SLIF monitor the microscopic motion caused by
intracellular calcium oscillations in the intact heart. We measured SLIF
from rat hearts during 60 min of global ischemia at 30 degrees C, followed
by reflow. Ischemia reduced SLIF frequency to zero within 30 min. Reflow
caused an overshoot of SLIF frequency to as much as five times control,
suggesting that reflow causes major calcium overload of cells that are at
least transiently viable.
