RESUMO
The aim of current study was to determinate ex vivo and chromatographic fingerprint by HPLC of four extracts of Euphorbia furcillata K. Ethyl acetate extract of Euphorbia furcillata (EaEEf) was the most effective and potent extract (Emax=98.69±1.24%) and its effect was partially endothelium-dependent. Functional vasorelaxant mechanism of action of EaEEf was determinate, EaEEf showed efficient relaxation of KCl [80 mM]-induced contraction and norepinephrine and CaCl2 contraction curves showed diminution of maximal contraction in the presence of EAEEf and EaEEf-relaxation curve was shifted to the right in the presence of L-NAME (nitric oxide synthase inhibitor) and ODQ (guanylate cyclase inhibitor). Chromatographic fingerprints analysis suggests presence of diterpenoid such as abietane, tigliane, and ingenane skeletons. Our experiments suggest the EaEEf vasorelaxant activity could be attributed to diterpenoid molecules whose mechanism involves nitric oxide production and calcium channel blockade.
Se determinoÌ el efecto vasorrelajante ex vivo y los perfiles cromatograÌficos mediante HPLC de cuatro extractos de Euphorbia furcillata K.. El extracto de acetato de etilo de E. furcillata (EaEEf) fue el maÌs eficaz y potente en la contraccioÌn inducida por norepinefrina (Emax=98.69±1.24%) y el efecto fue parcialmente dependiente del endotelio vascular. Se determinoÌ el mecanismo de accioÌn vasorrelajante para EaEEf, este mostroÌ ser eficaz sobre la contraccioÌn inducida por KCl [80 mM] y la curva de contraccioÌn en respuesta a norepinefrina y CaCl2 en presencia de EaEEf mostroÌ disminucioÌn en la contraccioÌn maÌxima, mientras que la curva de relajacioÌn de EaEEf en presencia de L-NAME (inhibidor de oÌxido niÌtrico sintasa) y ODQ (inhibidor de guanilato ciclasa) se desplazoÌ hacia la derecha. El anaÌlisis cromatograÌfico de EaEEf sugiere la presencia de moleÌculas diterpenoides como abietano, tigliano y esqueletos de ingenano. Nuestros resultados sugieren que el efecto vasorrelajante de EaEEf podriÌa atribuirse a moleÌculas diterpenoides, cuyo mecanismo de accioÌn involucra la produccioÌn de oÌxido niÌtrico y bloqueo de canales de calcio.
Assuntos
Animais , Masculino , Ratos , Vasodilatadores/farmacologia , Extratos Vegetais/farmacologia , Euphorbia/química , Bloqueadores dos Canais de Cálcio/metabolismo , Cromatografia Líquida de Alta Pressão , Ratos Wistar , GMP Cíclico/metabolismo , Óxido Nítrico/metabolismoRESUMO
This study aims to investigate the mechanism of relaxant action of Ethyl 6-amino-5-cyano-2-methyl-4-(pyridin- 4-yl)- 4H-pyran-3-carboxylate (1) in in silico study and ex vivo tracheal rat rings pre-contracted with carbachol (1 µM). Compound 1 was more active than theophylline [a phosphodiesterases (PDE’s) inhibitor] used as positive control. Moreover, pretreatment with 1 significantly shifted to the right the carbachol-induced contraction and did not allow to reach the maximum effect (p< 0.001). In addition, compound 1 (96.30 µM) produces significant (100%) relaxant effect on the contraction induced by KCl (80mM), and the CaCl2-induced contraction was completely abolished by 1 as nifedipine does (a L-type calcium channel blocker), used as positive control (p< 0.001). Meanwhile, in the presence of isoproterenol (a β-adrenergic agonist), propranolol (a β-adrenergic antagonist), and K+ channel blocker 2-AP the relaxant curve was significantly modified (p< 0.05). Compound 1 was docked on an outer cavity located on the intracellular side of the human L-type calcium channel model and interacts in the following chains and residues: chain IP (G51, W52, T53, D54), IVP (R45, E50, A51, Q53, D54) and IS6 (W4, F7). In conclusion, ex vivo and in silico approaches suggest that compound 1 induces its relaxant effect mainly by calcium channel blockade, but other mechanisms like potassium channel and cAMP accumulation could be involved.
RESUMO
With patch clamp method,the effects of taurine (Tau) on slow inward calcium current (Ica) were investigated in single ventricular cells of guinea pigs. Tau decreased Ica in a dose- and voltage-dependent mode,but had little effect on reversal potential. Tau 0. 1 umol - L-1 decreased Ica by 17% and its maximal effective concentration was near 100 umol -L '. The initial block of Tau had already reached by 47% after a rest out of stimulation. Tau facilitated the reduction of lea through increasing clamp pulse frequency. The obtained results suggested that it decreased Ica in a use-dependent manner.