Role of endothelium on Vasorelaxant effect of Ribes biebersteinii fruit total extract on rat isolated aorta

Ribes biebersteinii fruit is used for treatment of hypertension in folk medicine of Azarbaijan. However it's mechanism of action is not studied. This work was aimed to examine the vasorelaxant effect of the Ribes biebersteinii fruit total extract (RBE) and role of endothelium in rat isolated aorta. Rings of aorta (3-5 mm length) were prepared and equilibrated in Kreb's solution under 2 g tension. Rings with or without endothelium were contracted by phenylephrine (PHE, 0.1μM) or PGF2α (8 μM) and then exposed to cumulative doses of RBE. In order to asses the role of endothelium in the vasorelaxant effect of RBE, tissues were studied by incubation for 20 min by (L-NAME, 100 μM) or (Methylene blue, 10μM) before contraction by PHE. RBE induced relaxation in rat aortic rings pre-contracted with PHE or PGF2α dose–dependently in both intact and endothelium-denuded aortic rings. The differences between the relaxant response of intact and endothelium denuded rings were not significant (p>0.05). L-NAME and Methylene blue did not affect the RBE-induced relaxant response in rat aortic rings. the results indicate that RBE induces relaxation dose-dependently in rat aortic rings precontracted with PHE by a mechanism independent of endothelium function or its productions.