Changes of action potentials and ion currents in neonatal rat
ventricular myocytes during long-term primary culture.
Guo, Weinong, Kaichiro Kamiya, Jianhua Cheng, and Junji Toyama.
Department of Circulation, Division of Regulation of Organ
Function, Research Institute of Environmental Medicine, Nagoya
University, Nagoya 464-01, Japan
APStracts 3:0030C, 1996.
A primary culture of neonatal ventricular myocytes isolated from day
-old rats was established for investigating the changes in action
potentials and ion currents over long periods. Cells at days 5 and 15
in culture were studied. These changes in vitro were compared to
those in situ derived from the age-matched freshly isolated cells.
During primary culture, quiescent cells demonstrated shortening of
action potential durations (APD) resembling the developmental changes
observed in situ. The beating cultured cells were not associated with
APD shortening. Despite of constant current amplitudes, the densities
of Ca2+ currents (ICa) decreased in the quiescent cultures at later
ages as a result of cell enlargement. ICa densities were maintained
in the beating cultured and freshly isolated cells. Acceleration in
the inactivation of ICa was observed during developments both in
vitro and in situ. In addition, the densities of transient outward
currents (Ito) tripled and doubled in the quiescent and beating cells
during 15-day cultures. However, Ito in beating cultured cells made
less contribution to APD, in contrast to the quiescent cultured and
freshly isolated myocytes. These findings demonstrate that
electrophysiological properties differ between two types of long-term
cultured cells. ICa densities remained constant in the beating
cultures suggesting that cell beating may be required for the
maintenance of ICa density in developing cardiomyocytes.
Received 18 July 1995; accepted in final form 5 January 1996.
APS Manuscript Number C433-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96