Vascular effects of 7-epiclusianone, a prenylated benzophenone from Rheedia gardneriana, on the rat aorta.

Abstract

The vascular effects of 7-epiclusianone on the rat aorta were investigated. In the rat aortic rings with functional endothelia, 7-epiclusianone up to 10mM induced a concentration-dependent vasodilatation of the sustained con tractions induced by phenylephrine (0.3mM). At concentrations higher than 10mM, 7-epiclusianone induced a concentration-dependent contraction in the aortic rings . The vasodilator effect of 7 -epiclusianone was drastically decreased with L-NAME (100m M) as well as in endothelium-denuded aortic rings. Moreover, indo methacin (10mM) induced a significant shift to the left in the vasodilator but did not modify the vasoconstrictor effect of 7-epiclusianone. In arteries without pre-contraction, 7-epi clusianone (3–100 m M) induced concentration-dependent contraction only in endothelium- intact an d in the presence of L-NAM E (100 m M). This effect was inhibited by indomet hacin (10mM ) and ZM2 30487 (1 mM), selective inhibitors of cyclooxygenase and of 5-lipoxygenase, respectively. We can conclude that at low concentrations 7 -epiclusianone induces an endothelium-dependent vasodilator effect in rat aortic rings . At higher concentrations an d in conditions where NO synthase was inhibited, 7-epiclusianone induces a vasocontractile effect. Nitric oxide seems to participate in the vasodilatation , while endothelial cyclooxygenase and 5 -lipoxygenase-derived products play a role in the vasoconstrictor effect.