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KMID : 0370220140580040245
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Yakhak Hoeji
2014 Volume.58 No. 4 p.245 ~ p.249
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Enhancement of Ca2+ Spark Occurrence by Murrayafoline-A in Rat Ventricular Myocytes
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Kim Joon-Chul
Nguyen Manh Cuong
Woo Sun-Hee
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Abstract
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Murrayafoline-A (1-methoxy-3-methylcarbazole) is a monomeric carbazole alkaloid found in Murraya euchrestifolia HAYATA and Glycosmis stenocarpa. We have recently shown that murrayafoline-A has positive inotropic effect in isolated
rat ventricular myocytes. To know possible mechanisms for the positive inotropic effect of murrayafoline-A we examined the effects of murrayafoline-A on in situ behavior of cardiac Ca2+ release units (‘Ca2+ sparks’) and sarcoplasmic reticulum (SR) Ca2+ loading using confocal Ca2+ imaging method in single rat ventricular myocytes. Murrayafoline-A significantly
increased the frequency (events/(103 μm2 · s)) of Ca2+ sparks in a concentration-dependent manner, with an EC50
of 28±6.4 μM and a maximal ~twofold change. The Ca2+ content in the SR, measured as caffeine (10 mM)-induced Ca2+
transient, was significantly increased by murrayafoline-A (?116% and ?123% of control at 25 and 100 μM, respectively). In
addition, murrayafoline-A significantly increased the fractional Ca2+ release, suggesting increase in the efficacy of Ca2+
release at given SR Ca2+ loading. These results suggest that murrayafoline-A may enhance contractility via increase in Ca2+ release from the SR through the ryanodine receptors in ventricular myocytes.
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KEYWORD
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murrayafoline-A, Ca2+ spark, ventricular myocytes, SR Ca2+ content, fractional Ca2+ release
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