Action potentials, contraction, and membrane currents in guinea pig ventricular preparations treated with the antispasmodic agent terodiline

Lesya M. Shuba, Yuji Kasamaki, Stephen E. Jones, Toshitsugu Ogura, John R. McCullough, Terence F. McDonald

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Terodiline was widely prescribed for urinary incontinence before reports of adverse cardiac effects that included bradycardia, QT lengthening, and ventricular tachyarrhythmia. The present study on guinea pig papillary muscles and ventricular myocytes was undertaken to gain insight into the cardioactive properties of the drug. Clinically relevant concentrations (<10 μM) of terodiline lengthened the action potential duration by up to 12%; higher concentrations shortened the duration in a concentration-dependent manner. The drug depressed maximal upstroke velocity in a use-dependent manner; the IC50 value was near 150 μM in muscles driven at 1 Hz, 60 μM at 3 Hz, 38 μM at 5 Hz, and 3 μM at 1 Hz in muscles depolarized with 14 mM K+. Submicromolar terodiline frequently had a small positive inotropic effect, whereas micromolar concentrations depressed force in a frequency- dependent manner. Voltage-clamp results on myocytes indicate that terodiline inhibits three membrane currents that govern repolarization: 1) E4031- sensitive, rapidly activating K+ current with an IC50 value near 0.7 μM as previously reported; 2) slowly activating, delayed-rectifier K+ current with an IC50 value of 26 μM; and 3) L-type Ca2+ current with an IC50 value of 12 μM. These findings are correlated with the changes in action potential configuration and developed tension and discussed in relation to the cardiotoxic effects of the drug.

Original languageEnglish
Pages (from-to)1417-1426
Number of pages10
JournalJournal of Pharmacology and Experimental Therapeutics
Volume290
Issue number3
Publication statusPublished - Sept 1999

ASJC Scopus Subject Areas

  • Molecular Medicine
  • Pharmacology

Fingerprint

Dive into the research topics of 'Action potentials, contraction, and membrane currents in guinea pig ventricular preparations treated with the antispasmodic agent terodiline'. Together they form a unique fingerprint.

Cite this