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Centre National de la Recherche Scientifique, UMR 6558, Laboratoire des Biomembranes et Signalisation Cellulaire, Faculty of Sciences, University of Poitiers, 86022 Poitiers cedex, France
Calcium current was recorded
from ventricular cardiomyocytes of rats at various stages of postnatal
development using the whole cell patch-clamp technique. In cultured
3-day-old neonatal cells, the current carried by Ca2+ or
Ba2+ (5 mM) was not completely inhibited by 2 µM
nifedipine. A residual current was activated in the same voltage range
as the L-type, nifedipine-sensitive Ca2+ current, but its
steady-state inactivation was negatively shifted by 16 mV. This
nifedipine-resistant calcium current was not further inhibited by other
organic calcium current antagonists such as PN200-110, verapamil, and
diltiazem nor by nickel,
-conotoxin, or tetrodotoxin. It was
completely blocked by cadmium and increased by isoproterenol and
forskolin. This current was >20% of total calcium current in
ventricular myocytes freshly isolated from neonatal rats, and it
decreased during postnatal maturation, disappearing at the adult stage.
This suggests that this current could be caused by an isoform of the
L-type calcium channel expressed in a way that reflects the
developmental stage of the rat heart.
rats; heart; development; Ca2+ channel isoform
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