Vasodilatory effects of mulberry (Morus spp.) leaf extract on porcine cerebral arteries in vitro: Possible underlying mechanisms.

Vasodilatory effects of mulberry leaf extract (MLE) and its possible underlying mechanisms on porcine basilar artery (PBA) were investigated by measuring changes in isometric tension in vitro . MLE slightly relaxed 60 mM KCl pre-contracted PBA rings (9.4% at 540 μg/mL). A treatment with MLE induced extensive relaxation under pre-contraction with 0.1 μM U-46619 (EC 50 = 49.4 μg/mL). Neither endothelial denudation nor treatment with atenolol (10 μM) affected MLE-induced relaxation. Relaxation induced by MLE (540 μg/mL) was significantly attenuated by cimetidine (10 μM). MLE inhibited angiotensin I-induced contraction in endothelium-intact PBA rings (EC 50 = 25 μg/mL), similar to captopril. Therefore, the possible mechanisms underlying MLE-induced relaxation in PBA might be mediated through: (1) functional antagonism of thromboxane A 2 receptors; (2) suppression of angiotensin I-induced contraction; (3) Ca 2+ influx inhibition; (4) stimulation of H 2 -receptors. Moreover, MLE contained significant amounts of nitrite, nitrate and several phenolic compounds, possibly associated with MLE-induced relaxation. [ABSTRACT FROM AUTHOR]