Electrophysiological effects of protopine in cardiac myocytes: inhibition of multiple cation channel currents

British Journal of Pharmacology
L S SongH Cheng

Abstract

Protopine (Pro) from Corydalis tubers has been shown to have multiple actions on cardiovascular system, including anti-arrhythmic, anti-hypertensive and negative inotropic effects. Although it was thought that Pro exerts its actions through blocking Ca(2+) currents, the electrophysiological profile of Pro is unclear. The aim of this study is to elucidate the ionic mechanisms of Pro effects in the heart. In single isolated ventricular myocytes from guinea-pig, extracellular application of Pro markedly and reversibly abbreviates action potential duration, and decreases the rate of upstroke (dV/dt)(max), amplitude and overshoot of action potential in a dose-dependent manner. Additionally, it produces a slight, but significant hyperpolarization of the resting membrane potential. Pro at 25, 50 and 100 microM reduces L-type Ca(2+) current (I(Ca,L)) amplitude to 89.1, 61.9 and 45.8% of control, respectively, and significantly slows the decay kinetics of I(Ca,L) at higher concentration. The steady state inactivation of I(Ca,L) is shifted negatively by 5.9 - 7.0 mV (at 50 - 100 microM Pro), whereas the voltage-dependent activation of I(Ca,L) remains unchanged. In contrast, Pro at 100 microM has no evident effects on T-type Ca(2+) curren...Continue Reading

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Citations

Jul 12, 2011·The Journal of Membrane Biology·Guanghua TangRui Wang
Feb 6, 2004·European Journal of Pharmacology·Liane D PaulHans H Maurer
Aug 4, 2004·Progress in Biophysics and Molecular Biology·William BainsCat White
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Jul 27, 2007·Basic & Clinical Pharmacology & Toxicology·Xianghua XiaoYuanhui Zhang
Dec 14, 2004·European Journal of Pharmacology·Bo JiangRui Wang
Sep 14, 2016·International Journal of Molecular Sciences·Andrew CroakerLei Liu
Oct 22, 2003·Journal of Biomolecular Screening·Christian WolffPierre Chatelain
May 11, 2005·Magnetic Resonance in Chemistry : MRC·Jaromír TousekRadek Marek

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