The effect of xanthone on smooth muscle was studied in thoracic aorta isolated from rats. Xanthone relaxed the norepinephrine-induced contraction of rat thoracic aorta. This relaxing effect of xanthone persisted in endothelium-denuded aorta suggesting that the relaxation induced by xanthone is endothelium-independent. The norepinephrine and high-K+-induced vasoconstriction was inhibited dose dependently in aorta pretreated with xanthone with IC50 values of 60.26 ± 8.43 and 82.9 ± 13.21 μM, respectively. The inositol 1,4,5-trisphosphate formation induced by norepinephrine (3 μM) in rat aorta was not affected by xanthone (10-100 μM), suggesting that the vasorelaxant effect of xanthone was not exerted on the receptor. Xanthone concentration dependently inhibited the 45Ca2+ influx induced by either norepinephrine or high-K+, suggesting that xanthone might act as a blocker of both receptor-operated and voltage-dependent Ca2+ channels. Furthermore, xanthone caused an increase in the level of intracellular cyclic adenosine 3',5'-monophosphate (cAMP), but not cyclic guanosine 3',5'-monophosphate (cGMP) content. These data suggested that the mechanism of xanthone-induced vasorelaxation might involve the increase of intracellular cyclic adenosine 3',5'-monophosphate (cAMP) content and block of Ca2+ channels.

Original languageEnglish
Pages (from-to)23-28
Number of pages6
JournalEuropean Journal of Pharmacology
Issue number1
Publication statusPublished - Oct 1 1997


  • Ca channel blocker
  • Norepinephrine
  • Thoracic aorta
  • Vasorelaxation
  • cAMP
  • cGMP

ASJC Scopus subject areas

  • Pharmacology


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