AJP - Cell Physiology, Vol 237, Issue 1 87-C95, Copyright © 1979 by American Physiological Society
Electrical activity of rat myocardial cells in culture: La3+-induced alterations
M. C. Kitzes and M. W. Berns
Intracellular analysis of neonatal rat (1-2 day old) ventricular cells in
culture shows that contracting myocardial cells exhibit an array of
different patterns of spontaneous electrical activity. Resting membrane
potentials varied between -40 mV and -98 mV. Our results indicate that some
cultured cells show resting membrane potentials, overshoot, and total spike
amplitude values comparable to those normally found in neonatal and adult
rat heart. A low ratio of pacemaker (40%) to nonpacemaker cells (60%) and
low incidence of hyperpolarizing after-potentials (35%) were found. La3+
application (0.1-4.0 mM) induced progressive cell depolarization,
concomitant diminution in discharge frequency, and marked alteration of
action potential configuration. A parallel decline in frequency and
strength of rhythmic contractions was observed. Abolition of contractility
occurred only in association with depolarization and complete disappearance
of action potentials. Recovery of electrical and contractile activity
followed medium replacement. Our results indicate that La3+ does not act as
a specific excitation-contraction (E-C) uncoupler in the cultured cells but
has multiple effects upon their normal electrical characteristics.
