Endothelium-dependent vasorelaxing activity of aqueous extracts of Ilex paraguariensis on mesenteric arterial bed of rats

The effects of aqueous extracts of Ilex paraguariensis leaves (AEIp) were studied. Mesenteric arterial bed (MAB), precontracted by methoxamine with or without intact endothelium, was mounted on a tissue bath and exposed to plant extracts (bolus). The bolus injections of AEIp (300-1050 mu g) significantly inhibited, in a concentration-dependent manner, the maximal contractile response induced by methoxamine (30 mu m) in MAB. The endothelium-dependent relaxations were reversed by N-G-nitro-L-arginine methyl ester (10 mM), whereas methylene blue (100 mu M) was not capable of effectively inhibiting the AEIp-induced vasodilatation of MAB. The vasorelaxing effect of AEIp, persisted in the presence of indomethacin (10 mu M). These results suggest the involvement of NO of endothelial source (Or others factors) in this vasodilatory effect. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.