The methanolic extract of leaves of Michelia figo Spreng. (Magnoliaceae), as well as several purified fractions, showed a concentration-dependent vasorelaxing effect on aortic rings endothelium-deprived and pre-contracted by norepinephrine (NE). For further pharmacological investigation on the mechanism of action, the fraction S4 was selected, since it showed the best vasodilator properties. The pharmacological effect was not produced through the stimulation of cyclooxygenase, adenyl cyclase, or guanylyl cyclase, since selective inhibitors did not prevent the fraction S4-induced effects. Moreover, the vasorelaxing effect of the fraction was resistant to the block of nifedipine-sensitive Ca2+ channels. The fraction S4 (10(-4) g/ml) produced a shift towards the right of the concentration-contractile response curve to NE, in normal conditions, and the shift was more evident in Ca2+-free Tyrode Solution, Suggesting an action on intracellular Ca2+-channels. The vasodilator action of fraction S4 on NE pre-contracted rings was not prevented by cyclopiazonic acid (blocker of Ca2+/ATPase), which excludes a role for mechanisms involving the storage of Ca2+ in the sarcoplasmic reticulum. The reduction of the contraction elicited by caffeine, an opener of ryanodine-sensitive receptors suggests that the fraction S4 of Michelia figo leaves could produce the vasorelaxing response by the blockade of ryanodine-sensitive Ca2+ channels of the sarcoplasmic reticulum. (C) 2004 Elsevier Ireland Ltd. All rights reserved.
VASODILATOR ACTIVITY OF MICHELIA FIGO SPRENG (MAGNOLIACEAE) BY IN VITRO FUNCTIONAL STUDY
CHERICONI S;TESTAI, LARA;CALDERONE, VINCENZO;
2004-01-01
Abstract
The methanolic extract of leaves of Michelia figo Spreng. (Magnoliaceae), as well as several purified fractions, showed a concentration-dependent vasorelaxing effect on aortic rings endothelium-deprived and pre-contracted by norepinephrine (NE). For further pharmacological investigation on the mechanism of action, the fraction S4 was selected, since it showed the best vasodilator properties. The pharmacological effect was not produced through the stimulation of cyclooxygenase, adenyl cyclase, or guanylyl cyclase, since selective inhibitors did not prevent the fraction S4-induced effects. Moreover, the vasorelaxing effect of the fraction was resistant to the block of nifedipine-sensitive Ca2+ channels. The fraction S4 (10(-4) g/ml) produced a shift towards the right of the concentration-contractile response curve to NE, in normal conditions, and the shift was more evident in Ca2+-free Tyrode Solution, Suggesting an action on intracellular Ca2+-channels. The vasodilator action of fraction S4 on NE pre-contracted rings was not prevented by cyclopiazonic acid (blocker of Ca2+/ATPase), which excludes a role for mechanisms involving the storage of Ca2+ in the sarcoplasmic reticulum. The reduction of the contraction elicited by caffeine, an opener of ryanodine-sensitive receptors suggests that the fraction S4 of Michelia figo leaves could produce the vasorelaxing response by the blockade of ryanodine-sensitive Ca2+ channels of the sarcoplasmic reticulum. (C) 2004 Elsevier Ireland Ltd. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
