Evaluation of T- and L-type Ca2+ currents in shark ventricular myocytes

James Maylie, M. Morad

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Abstract

Two types of Ca2+ currents with characteristics of T- and L-type Ca2+ currents were recorded in ventricular myocytes of dogfish (Squalus acanthias). The T-type Ca2+ current activated near -70 mV and had a peak current density of 9.8 pA/pF at -34 mV. The L-type Ca2+ current activated near -50 mV and had a peak current density of 10.6 pA/pF near 0 mV. The threshold for activation of the T-type Ca2+ current was 20 mV negative to that of the tetrodotoxin-sensitive Na+ current. Inactivation of the T-type Ca2+ current was rapid with a limiting time constant of 5 ms at positive potentials. The T-type Ca2+ current was not modulated by isoproterenol or acetylcholine. In dogfish the T-type Ca2+ channel has current densities equivalent to the L-type channel and is likely to activate before the Na2+ channel, contributing significantly to generation of the foot of the action potential.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume269
Issue number5 38-5
Publication statusPublished - 1995

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Keywords

  • β-adrenergic and cholinergic regulation of calcium channel
  • dogfish
  • dogfish heart
  • Squalus acanthias

ASJC Scopus subject areas

  • Physiology
  • Agricultural and Biological Sciences(all)

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