Effects of cyclopiazonic acid on membrane currents, contraction and intracellular calcium transients in frog heart

Journal of Molecular and Cellular Cardiology
A BadaouiC Léoty

Abstract

The effects of cyclopiazonic acid, a specific inhibitor of the sarcoplasmic reticulum Ca(2+)-ATPase, on membrane currents and contraction were investigated under voltage clamped conditions on frog atrial trabeculae using the double mannitol-gap technique. In ringer solution, cyclopiazonic acid (10 microM) decreased the phasic contraction at all levels of depolarization without significant change in the time to peak of the contraction and time constant of relaxation. In a low-sodium the amplitude and the current/voltage relationship of L-type and T-type Ca2+ currents were not modified while their inactivation phase was markedly slowed by cyclopiazonic acid. At all levels of depolarization the tonic contraction was increased by cyclopiazonic acid. In the presence of cyclopiazonic acid, no significant variation in diastolic level of intracellular calcium ([Ca2+]i) was found while the maximum amplitude of the Ca2+ transient associated with an action potential was reduced and its time course slowed. All the reversible changes observed could be interpreted by assuming that, in frog atria, sarcoplasmic reticulum was present and cyclopiazonic acid inhibits the sarcoplasmic reticulum Ca(2+)-ATPase. It is proposed that under normal condi...Continue Reading

Citations

Jan 1, 1996·Basic Research in Cardiology·U BavendiekR H Schwinger
Dec 1, 1996·Comparative Biochemistry and Physiology. Part A, Physiology·V Bonnet, C Léoty
Nov 4, 2008·Experimental Physiology·Nina S GhaisChristopher L-H Huang
Feb 9, 2011·Journal of Cellular Physiology·André Soares LeopoldoAntonio Carlos Cicogna
Apr 20, 2017·Brazilian Journal of Medical and Biological Research = Revista Brasileira De Pesquisas Médicas E Biológicas·C F S M P SilveiraA C Cicogna
Sep 24, 2005·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Matti Vornanen

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