Abstract
The chloroformic crude extract of roots of
Bupleurum fruticosum L. (Umbelliferae) showed a concentration-dependent vasorelaxing effect on aortic rings endothelium-deprived and pre-contracted by norepinephrine (NE).
The pharmacological effect was not produced through the stimulation of cyclooxygenase, adenyl cyclase, or guanylyl cyclase, since selective inhibitors did not prevent the extract-induced responses.
The incubation of the aortic rings with the chloroformic extract (10
−4
g/ml) produced a depression of the concentration–contractile response curve to NE, in normal conditions, and this effect was more evident in Ca
2+-free Tyrode solution, suggesting an action on the intracellular mobilization of Ca
2+ ions.
Moreover, the vasodilator action of
Bupleurum fruticosum extract was resistant to the pre-treatment with nifedipine and to the pre-treatment with cyclopiazonic acid (blocker of Ca
2+/ATPase).
Finally, the chloroformic extract of
Bupleurum fruticosum produced a reduction of the contraction obtained by caffeine, an opener of ryanodine-sensitive receptors, suggesting that the plant could elicit the vasorelaxing response by the blockade of ryanodine-sensitive Ca
2+ channels of the sarcoplasmic reticulum.