RESUMO
We examined the inhibitory effects of α-linolenic acid (ALA) on the contractions of pig coronary arteries. ALA concentration-dependently inhibited the contractions elicited by U46619 and prostaglandin F2α without affecting those elicited by 80 mM KCl, histamine, acetylcholine, and serotonin. ALA rightward shifted the concentration-response curve of U46619, and Schild plot analysis revealed that ALA competitively antagonized U46619. Furthermore, ALA inhibited the increase in intracellular Ca2+ concentration caused by TP receptor stimulation but not that caused by FP receptor stimulation. These results suggest that ALA behaves as a selective antagonist of TP receptors in coronary arteries.
Assuntos
Ácido 15-Hidroxi-11 alfa,9 alfa-(epoximetano)prosta-5,13-dienoico , Cálcio , Vasos Coronários , Receptores de Tromboxanos , Ácido alfa-Linolênico , Animais , Vasos Coronários/efeitos dos fármacos , Ácido alfa-Linolênico/farmacologia , Suínos , Ácido 15-Hidroxi-11 alfa,9 alfa-(epoximetano)prosta-5,13-dienoico/farmacologia , Cálcio/metabolismo , Receptores de Tromboxanos/antagonistas & inibidores , Receptores de Tromboxanos/metabolismo , Relação Dose-Resposta a Droga , Masculino , Dinoprosta/farmacologia , Contração Muscular/efeitos dos fármacosRESUMO
This study was performed to elucidate whether eicosapentaenoic acid (EPA) suppresses spasm-prone blood vessel contractions induced by a thromboxane mimetic (U46619) and prostaglandin F2α (PGF2α) and determine whether the primary target of EPA is the prostanoid TP receptor. Accordingly, we assessed: (1) the tension changes in porcine basilar and coronary arteries, and (2) changes in the Fura-2 (an intracellular Ca2+ indicator) fluorescence intensity ratio at 510 nm elicited by 340/380 nm excitation (F340/380) in 293T cells expressing the human TP receptor (TP-293T cells) and those expressing the human prostanoid FP receptor (FP-293T cells). EPA inhibited both porcine basilar and coronary artery contractions induced by U46619 and PGF2α in a concentration-dependent manner, but it did not affect the contractions induced by 80 mM KCl. EPA also inhibited the increase in F340/380 induced by U46619 and PGF2α in TP-293T cells. In contrast, EPA showed only a marginal effect on the increase in F340/380 induced by PGF2α in FP-293T cells. These findings indicate that EPA strongly suppresses the porcine basilar and coronary artery contractions mediated by TP receptor and that inhibition of TP receptors partly underlies the EPA-induced inhibitory effects on these arterial contractions.
