VASORELAXANT EFFECT OF THE ALKALOID 1-0-BENZOYLNAPPELINE ON ISOLATED RAT THORACIC AORTA
Annotatsiya
To investigate the possible mechanisms of vasorelaxant action of 1-O-benzoylnappeline (1-0-BN), a diterpenoid alkaloid napelline derivative.: The vasorelaxant activity of 1-0-BN was examined using standard organ bath techniques and endothelium intact rat aortic rings, precontracted by phenylephrine (PE) or by a high KCl (50 mM). 1-O-BN induced vasorelaxation, in rat aortic rings, precontracted by both PE and high KCl, in a concentrationdependent manner and with almost equal effectiveness. 1-O-BN significantly attenuated CaCl2induced contractions in a Ca2 +-free medium containing KCl (50 mM). Furthermore, the vasorelaxant potency of 1-O-BN significantly reduced in the presence of verapamil. 1-O-BN significantly reduced the transient contractions induced by PE or caffeine in Ca2+-free medium. The vasorelaxant effect of 1-O-BN progressively reduced with an elevation of KCl concentration (from 20 mM to 100 mM) and markedly attenuated by glibenclamide but not significantly affected by TEA, BaCl2, and 4-AP. Together, the results of the present study indicate that activation of KATP channels may play an important role in 1-O-BN induced vasorelaxation. The suppression of contractions induced by high KCl and by PE, in calcium-free medium, suggest that the inhibition of Ca2+ influx through voltage-dependent Ca2+ channels and Ca2+ release from intracellular stores also may be involved in the vasorelaxant effect of 1-O-BN.