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Green tea catechins evoke a phasic contraction in rat aorta via H2O2-mediated multiple-signalling pathways
Jian-Zhong Shen1, Xiu-Feng Zheng, Er-Qing Wei
1Department of Pharmacology, School of Medicine, Zhejiang University, Hubin Campus, Hangzhou, People's Republic of China.
Clinical and Experimental Pharmacology & Physiology
|January 25, 2003
Summary
Tea polyphenols and specific catechins like EGCG cause rat aorta contractions. This effect involves calcium signaling and a hydrogen peroxide pathway, mediated by the epigallol structure.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
- Biochemistry
Background:
- Tea polyphenols (TP) are known for various biological activities.
- Specific catechins, including epigallocatechin gallate (EGCG), are major components of tea.
- The direct effects of these compounds on vascular smooth muscle contractility require further elucidation.
Purpose of the Study:
- To investigate the contractile effects of tea polyphenols (TP) and their primary catechins on rat aorta.
- To identify the specific catechins responsible for the contractile effects and elucidate the underlying mechanisms.
- To determine the role of calcium ions and signaling pathways in TP-induced aortic contraction.
Main Methods:
- Isometric tension recording technique was used to measure rat aorta contractility.
- Concentration-response curves were generated for TP and its catechins (EC, ECG, EGC, EGCG).
- The study utilized various antagonists, chelators, and modulators to investigate signaling pathways, including calcium channels and intracellular calcium release.
Main Results:
- TP induced concentration-dependent phasic contractions of rat aorta, independent of the endothelium.
- EGCG and EGC mimicked the contractile response, suggesting the epigallol moiety is crucial.
- Contractions involved both intracellular and extracellular calcium, non-voltage-dependent calcium channels, intracellular calcium release, and a hydrogen peroxide-mediated pathway.
Conclusions:
- Tea polyphenols and catechins with an epigallol structure (EGCG, EGC) directly induce rat aortic smooth muscle contraction.
- The contractile effect is mediated by a hydrogen peroxide pathway involving calcium signaling.
- These findings provide novel insights into the cardiovascular effects of tea components.