Vasorelaxant effects and mechanisms of action of Heracleum sphondylium L. (Apiaceae) in rat thoracic aorta

Abstract

Ethnopharmacological relevance: Aerial parts of Heracleum sphondylium L. (HS) are used in traditional medicine to treat hypertension. To provide pharmacological basis for this use, we investigated the vasorelaxant effects of a dichloromethane extract of HS (HSDE) and the mechanisms involved.

Materials and methods: Activity of HSDE was evaluated on rat isolated thoracic aortic rings.

Results: HSDE induced vasorelaxation in phenylephrine (PE, 10(-6)mol/L) and high KCl-(6×10(-2)mol/L) pre-contracted aortic rings that was independent on the presence of endothelium. HSDE markedly decreased extracellular Ca(2+)-induced contraction in high-KCl and PE pre-challenged rings. It also inhibited the intracellular Ca(2+) release sensitive to PE (10(-6)M). The relaxant effect of HSDE were blunted by 4-amino-pyridine (4-AP, 10(-3)mol/L), an inhibitor of voltage-dependent K(+) channels.

Conclusion: Our results provide the first evidence that a dichloromethane extract of Heracleum sphondylium L. exhibits vasorelaxant properties through endothelium-independent mechanisms involving the inhibition of Ca(2+) mobilization and changes in Kv channel conductances. These data argue for its use as antihypertensive therapy in traditional medicine.