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Contractions Of The SHR Aorta To High Doses Of Epigallocatechin Gallate Are Due To Vasoconstrictor Prostanoids
Author(s) -
LI ZHUOMING,
KOO MARCEL W.L.,
MAN RICKY Y.K.,
VANHOUTTE PAUL M.
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.960.2
Subject(s) - chemistry , cyclooxygenase , thromboxane , prostanoid , epigallocatechin gallate , prostacyclin , thromboxane a2 , prostaglandin , stimulation , medicine , endocrinology , thromboxane b2 , receptor , pharmacology , antagonist , reactive oxygen species , catechin , enzyme , biochemistry , antioxidant , platelet , polyphenol
Objective Regular consumption of green tea is believed to be beneficial for the cardiovascular system. However, high concentrations of epigallocatechin gallate (EGCG), a catechin of green tea, cause contractions of the aorta of spontaneously hypertensive rats (SHR). The present studies were designed to investigate the mechanisms underlying these EGCG‐induced contractions. Methods Isometric tension was measured in isolated aortic rings from 36‐weeks‐old male SHR. The release of prostanoids end‐products was measured with enzyme immunoassay kits. The intracellular reactive oxygen species (ROS) concentration was measured by confocal microscopy. Results From 10 −6 to 10 −4 M, EGCG induced concentration‐dependent contractions in preparations with and without endothelium. These contractions were abolished by cyclooxygenase (COX) inhibitor indomethacin or the thromboxane‐prostanoid (TP) receptor antagonist S18886, and reduced by antioxidants. The release of prostaglandin F 1α , prostaglandin F 2α and thromboxane B 2 was significantly increased by 10 −4 M EGCG. A burst of ROS was observed upon exposure to 10 −4 M of EGCG. Conclusions The EGCG‐induced contractions involve the production of ROS, activation of COX, production of prostanoids and stimulation of TP receptors. This study indicates a possible adverse effect of EGCG administration and tea consumption at high concentrations.