T-type calcium current in latent pacemaker cells isolated from cat right atrium

Zhengfeng Zhou, Stephen L. Lipsius

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


Whole-cell voltage clamp techniques were used to study Ca2+ currents in latent pacemaker cells isolated from cat right atrium. T-type (ICa, T) and L-type (ICa, L) Ca2+ currents were distinguished by their voltage dependence of activation, and sensitivity to channel blocking agents. In 2.7 mM [Ca]o, ICa, T activation exhibited a voltage threshold of about −50mV and maximum amplitude at −10mV, whereas ICa, L threshold was about −30mV and maximum amplitude was at +10mV. The half-maximal activation voltages of ICa, T was −31.4±0.2mV and ICa, T was −6.2±2.0mV. Overlap of the steady-state activation-inactivation curves for ICa, T showed a “window” current at voltages compatible with the late phase of diastolic depolarization. Maximum ICa, T and ICa, L current densities were 3.3 ±0.4pA/pF and 12.5 ±1.3pA/pF, respectively. ICa, T current density in working atrial muscle cells was 0.73 ±0.31pA/pF. Both ICa, L and ICa, T were blocked by 2mM cobalt. ICa, L but not ICa, T was blocked by 1 μM nifedipine. Nickel (Ni2+: 40 μM) inhibited ICa, T primarily at more negative voltages. In addition, Ni2+ decreased the late phase of diastolic depolarization and significantly increased pacemaker cycle length. These results indicate that latent atrial pacemaker cells exhibit ICa, T that is significantly larger in amplitude than in working atrial muscle cells. ICa, T may contribute current during the late phase of diastolic depolarization. Because latent pacemakers exhibit a more negative maximum diastolic potential, ICa, T may contribute more to latent than to primarypacemaker activity.

Original languageEnglish (US)
Pages (from-to)1211-1219
Number of pages9
JournalJournal of molecular and cellular cardiology
Issue number9
StatePublished - Sep 1994
Externally publishedYes


  • Calcium channels
  • Cobalt
  • Nickel
  • Nifedipine
  • Nystatin perforated-patch
  • Whole-cell patch clamp

ASJC Scopus subject areas

  • Molecular Biology
  • Cardiology and Cardiovascular Medicine


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