Artemisia herba-alba Asso relaxes the rat aorta through activation of NO/cGMP pathway and K_ATP channels

Abstract

Artemisia herba-alba Asso (Compositae) is used in oriental Morocco to treat diabetes and arterial hypertension. The present work evaluated the vasorelaxant effect of Artemisia herba-alba aqueous extract (AHAE) in isolated rat aorta and the mechanism underlying this effect. In endothelium-containing aorta preparations, AHAE (10^–3, 10^–2, 10^–1, 1 and 2 mg/mL) relaxed the contraction elicited by noradrenaline in a concentration-dependent manner. This effect is dependent upon integrity of the vascular endothelium as it was fully abolished in endothelium-denuded preparations. The vasorelaxant effect of AHAE (2 mg/mL) was also inhibited by N^G-nitro-L-arginine methyl-ester (100 μM), methylene blue (10 μM) or 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (50 μM) but not by 10 μM atropine. This effect remained unchanged by tetraethylammonium (5 mM) or indomethacin (10 μM) whereas it was significantly attenuated by glibenclamide (10 μM). These results suggest that AHAE produces an endothelium-dependent relaxation of the isolated rat aorta, an effect that seems mainly mediated through stimulation of the endothelial nitric oxide synthase by mechanisms other than activation of muscarinic receptors. Activation of ATP-dependent potassium channels partly contributes in the mediation of AHAE-induced endothelium-dependent relaxation.