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Title: Channels involved in transient currents unmasked by removal of extracellular calcium in cardiac cells
Authors: Macianskiene, Regina ×
Moccia, Francesco
Sipido, Karin
Flameng, Willem
Mubagwa, Kanigula #
Issue Date: May-2002
Series Title: American Journal of Physiology. Heart and Circulatory Physiology vol:282 issue:5 pages:H1879-88
Abstract: In cardiac cells that lack macroscopic transient outward K(+) currents (I(to)), the removal of extracellular Ca(2+) can unmask "I(to)-like" currents. With the use of pig ventricular myocytes and the whole cell patch-clamp technique, we examined the possibility that cation efflux via L-type Ca(2+) channels underlies these currents. Removal of extracellular Ca(2+) and extracellular Mg(2+) induced time-independent currents at all potentials and time-dependent currents at potentials greater than -50 mV. Either K(+) or Cs(+) could carry the time-dependent currents, with reversal potential of +8 mV with internal K(+) and +34 mV with Cs(+). Activation and inactivation were voltage dependent [Boltzmann distributions with potential of half-maximal value (V(1/2)) = -24 mV and slope = -9 mV for activation; V(1/2) = -58 mV and slope = 13 mV for inactivation]. The time-dependent currents were resistant to 4-aminopyridine and to DIDS but blocked by nifedipine at high concentrations (IC(50) = 2 microM) as well as by verapamil and diltiazem. They could be increased by BAY K-8644 or by isoproterenol. We conclude that the I(to)-like currents are due to monovalent cation flow through L-type Ca(2+) channels, which in pig myocytes show low sensitivity to nifedipine.
ISSN: 0363-6135
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Experimental Cardiology
Experimental Cardiac Surgery
× corresponding author
# (joint) last author

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