Endothelium-independent vasorelaxant effect of dioclein, a new flavonoid isolated from Dioclea grandiflora, in the rat aorta.
We have investigated the endothelium-independent vasorelaxant effect of the new flavonoid dioclein (5,2',5'-trihydroxy-6-7-dimethoxyflavanone) in the rat aorta. In endothelium-denuded vessels, dioclein induced a concentration-dependent relaxation of aortic rings precontracted with noradrenaline (IC50 = 3.5+/-0.89 x 10(-4) M and KCl (IC50 = 5.2+/-1.2 x 10(-4) M). In the absence of extracellular calcium, dioclein reduced the contraction induced by noradrenaline (maximal reduction approximately 33%) but not that induced by caffeine. Dioclein also produced a concentration-dependent inhibition of the sustained contractions induced by the phorbol ester 12-O-tetradecanoyl phorbol-13-acetate in normal (IC50 = 4.0+/-0.2 x 10(-4) M) and Ca2+-free solution (IC50 = 4.0+/-0.3 x 10(-4) M). The results indicate that the endothelium-independent vasorelaxant effect of dioclein may be explained by inhibition of contractions dependent on activation of protein kinase C, voltage-dependent Ca2+ influx and on the release of intracellular Ca2+ stores sensitive to noradrenaline.
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Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.
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D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000502:physiology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D004727:Endothelium / Q000502:physiology; D044950:Flavanones; D005419:Flavonoids / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011493:Protein Kinase C / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology*
D000700:Analgesics; D015220:Calcium Channels; D044950:Flavanones; D005419:Flavonoids; D014665:Vasodilator Agents; C094747:dioclein; D011493:Protein Kinase C; D009638:Norepinephrine