Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/38378
標題: Differential effects of a green tea-derived polyphenol (-)-epigallocatechin-3-gallate on the acidosis-induced decrease in the Ca(2+) sensitivity of cardiac and skeletal muscle
作者: Liou, Y.M.
劉英明
Kuo, S.C.
Hsieh, S.R.
關鍵字: EGCg
green tea polyphenols
pH sensitivity
Ca(2+) sensitivity
troponin C
guinea-pig hearts
troponin-c
malignant hyperthermia
conformational-changes
angstrom resolution
agent emd-57033
calcium
ph
myofilaments
activation
期刊/報告no:: Pflugers Archiv-European Journal of Physiology, Volume 456, Issue 5, Page(s) 787-800.
摘要: (-)-Epigallocatechin-3-gallate (EGCg), a green tea-derived polyphenol, has received much attention as a protective agent against cardiovascular diseases. In this study, we determined its effects on the acidosis-induced change in the Ca(2+) sensitivity of myofilaments in myofibrils prepared from porcine ventricular myocardium and chicken pectoral muscle. EGCg (0.1 mM) significantly inhibited the decrease caused by lowering the pH from 7.0 to 6.0 in the Ca(2+) sensitivity of myofibrillar ATPase activity in cardiac muscle, but not in skeletal muscle. Studies on recombinant mouse cardiac troponin C (cTnC) and chicken fast skeletal troponin C (sTnC) using circular dichroism and intrinsic and extrinsic fluorescence spectroscopy showed that EGCg bound to cTnC with a dissociation constant of similar to 3-4 mu M, but did not bind to sTnC. By presumably binding to the cTnC C-lobe, EGCg decreased Ca(2+) binding to cTnC and overcame the depressant effect of protons on the Ca(2+) sensitivity of the cardiac contractile response. To demonstrate isoform-specific effects of the action of EGCg, the pH sensitivity of the Ca(2+) response was examined in cardiac myofibrils in which endogenous cTnC was replaced with exogenous sTnC or cTnC and in skeletal myofibrils in which the endogenous sTn complex was replaced with whole cardiac Tn complex (cTn). The results suggest that the binding of EGCg to the cardiac isoform-specific TnC or Tn complex alters the effect of pH on myofilament Ca(2+) sensitivity in striated muscle.
URI: http://hdl.handle.net/11455/38378
ISSN: 0031-6768
文章連結: http://dx.doi.org/10.1007/s00424-008-0456-y
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