Endothelium-independent vasorelaxation effects of 16-O-acetyldihydroisosteviol on isolated rat thoracic aorta |
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Authors: | Rungusa Pantan Amnart Onsa-ard Jiraporn Tocharus Orawan Wonganan Apichart Suksamrarn Chainarong Tocharus |
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Institution: | 1. Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand;2. Department of Biochemistry, Faculty of Medical Science, Phayao University, Phayao 56000, Thailand;3. Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand;4. Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand |
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Abstract: | AimsThe aim of this study is to investigate the vasorelaxant effect of 16-O-acetyldihydroisosteviol (ADIS) and its underlying mechanisms in isolated rat aorta.Main methodsRat aortic rings were isolated, suspended in organ baths containing Kreb's solution, maintained at 37 °C, and mounted on tungsten wire and continuously bubbled with a mixture of 95% O2 and 5% CO2 under a resting tension of 1 g. The vasorelaxant effects of ADIS were investigated by means of isometric tension recording experiment.Key findingsADIS (0.1 μM–3 mM) induced relaxation of aortic rings pre-contracted by phenylephrine (PE, 10 μM) and KCl (80 mM) with intact-endothelium (Emax = 79.26 ± 3.74 and 79.88 ± 3.79, respectively) or denuded-endothelium (Emax = 88.05 ± 3.69 and 78.22 ± 6.86, respectively). In depolarization Ca2+-free solution, ADIS inhibits calcium chloride (CaCl2)-induced contraction in endothelium-denuded rings in a concentration-dependent manner. In addition, ADIS attenuates transient contractions in Ca2+-free medium containing EGTA (1 mM) induced by PE (10 μM) and caffeine (20 mM). By contrast, relaxation was not affected by tetraethylammonium (TEA, 5 mM), 4-aminopyridine (4-AP, 1 mM), glibenclamide (10 μM), barium chloride (BaCl2, 1 mM), and 1H-1,2,3]oxadiazolo4,3-α]quinoxalin-1-one (ODQ, 1 μM).SignificanceThese findings reveal the vasorelaxant effect of ADIS, through endothelium-independent pathway. It acts as a Ca2 + channel blocker through both intracellular and extracellular Ca2 + release. |
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Keywords: | 16-O-Acetyldihydroisosteviol Vasorelaxation Endothelium-independent Aorta |
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