PARTICIPATION OF ADENYLYL CYCLASE/cAMP PATHWAY IN VASORELAXANT MECHANISM OF THE PYRANOCOUMARIN BRAYLIN IN MESENTERIC ARTERY

Abstract

IntroductionBraylin is a pyranocoumarin isolated from the species Zanthoxylum tingoassuiba (Rutaceae). Previous studies have shown that Braylin has a possible inhibitory action in phosphodiesterase enzymes.AimsThe aim of this study was to investigate the mechanism involved in the vasorelaxant effect of Braylin.MethodsThe experiments were performed using wistar rats (12–16 weeks/250–300g), euthanized in CO2 camera and the superior mesenteric artery were isolated and free from connective tissue and cut into rings (1–2 mm), suspended by cotton threads for isometric tension recordings in a Tyrode's solution at 37 °C, gassed with a 95% O2 and 5% CO2, under a resting tension of 0.75g. All surgical and experimental procedures were approved by the local Animal use and care ethics committee – CEUA/ICS/UFBA by the number 089/2015.ResultsThe cumulative administration of Braylin (0.1–300 μM) in phenylephrine (Phe 10μM) pre‐contracted mesenteric rings, induced a concentration‐dependent vasorelaxation (Emax = 111.5 ± 7.9%, CE50 = 4.8 (3.0 – 7.7) × 10−5, n = 17), the removal of the endothelium did not change this effect (Emax = 127.6 ± 13.1%, CE50 =1.7 (4.0 – 7.3) × 10−5, n = 16). The presence of ODQ (100 μM), an inhibitor of soluble guanylyl cyclase, also did not change the effect induced by Braylin (Emax = 117.3 ± 2.6%, CE50 = 1.3 (1.9 – 8.9) × 10−5, n = 5). On the other hand, the presence of SQ 22536, an adenylyl cyclase inhibitor, reduced the relaxant effect (Emax = 115.6 ± 2.8, CE50 = 4.3 (3.0 – 6.2) × 10−5, n = 5). The incubation of the superior mesenteric rings with KT‐5720, an inhibitor of PKA, reduced the effect of Braylin (Emax = 110.4 ± 5.3%, CE50 = 2.9 (2.0 – 4.1) × 10−5, n = 5). Pre‐treatment with KCl 20 mM, TEA (1mM), BaCl2 (30μM), or 4‐aminopiridin (1mM) decreased the pharmacological potency of the Braylin significantly.ConclusionThose effects taken together suggest that Braylin induces vasorelaxant effects in isolated superior mesenteric artery rings from normotensive involving AC/cAMP pathway. K+ channels also seem to be important in the relaxant effect, probably BKca channels.Support or Funding InformationFundação de Amparo à Pesquisado Estado da Bahia (fapesb) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)