The cloned cardiac Na channel α-subunit expressed in Xenopus oocytes show gating and blocking properties of native channels

Jonathan Satin, John W. Kyle, Michael Chen, Richard B. Rogart, Harry A. Fozzard

Research output: Contribution to journalArticlepeer-review

46 Scopus citations

Abstract

The neonatal rat cardiac Na channel α-subunit directed currents in oocytes show characteristic cardiac relative resistance to tetrodotoxin (TTX) block. TTX-sensitive currents obtained by expression in Xenopus oocytes of the α-subunits of the rat brain (BrnIIa) and adult skeletal muscle (μI) Na channels show abnormally slow decay kinetics. In order to determine if currents directed by the cardiac α-subunit (RHI) exhibit kinetics in oocytes like native currents, we compared RHI-directed currents in oocytes to Na currents in freshly isolated neonatal rat myocytes. The decay rate of RHI currents approached that of neonatal myocytes and was faster than BrnIIa and μI currents in oocytes. The voltage dependence of availability and activation was the same as that in the rat myocytes except for a 12-19 mV shift in the depolarizing direction. The RHI Na currents were sensitive to Cd2+ block, and they showed use dependence of TTX and lidocaine block similar to native currents. The current expressed in oocytes following injection of the cRNA encoding for the α-subunit of the cardiac Na channel possesses most of the characteristic kinetic and pharmacological properties of the native cardiac Na current.

Original languageEnglish
Pages (from-to)11-22
Number of pages12
JournalThe Journal of Membrane Biology
Volume130
Issue number1
DOIs
StatePublished - Oct 1992

Keywords

  • lidocaine
  • neonatal rat cardiac myocytes
  • patch clamp
  • sodium channels
  • tetrodotoxin

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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