8-11-14-eicosatrienoic-acid and arachidonyltrifluoromethane

The perivascular sensory nerve (PvN) Ca(2+)-sensing receptor (CaR) is implicated in Ca(2+)-induced relaxation of isolated, phenylephrine (PE)-contracted mesenteric arteries, which involves the vascular endogenous cannabinoid system. We determined the effect of inhibition of diacylglycerol (DAG) lipase (DAGL), phospholipase A(2) (PLA(2)), and cytochrome P-450 (CYP) on Ca(2+)-induced relaxation of PE-contracted rat mesenteric arteries. Our findings indicate that Ca(2+)-induced vasorelaxation is not dependent on the endothelium. The DAGL inhibitor RHC 802675 (1 microM) and the CYP and PLA(2) inhibitors quinacrine (5 microM) (EC(50): RHC 802675 2.8 +/- 0.4 mM vs. control 1.4 +/- 0.3 mM; quinacrine 4.8 +/- 0.4 mM vs. control 2.0 +/- 0.3 mM; n = 5) and arachidonyltrifluoromethyl ketone (AACOCF(3), 1 microM) reduced Ca(2+)-induced relaxation of mesenteric arteries. Synthetic 2-arachidonoylglycerol (2-AG) and glycerated epoxyeicosatrienoic acids (GEETs) induced concentration-dependent relaxation of isolated arteries. 2-AG relaxations were blocked by iberiotoxin (IBTX) (EC(50): control 0.96 +/- 0.14 nM, IBTX 1.3 +/- 0.5 microM) and miconazole (48 +/- 3%), and 11,12-GEET responses were blocked by IBTX (EC(50): control 55 +/- 9 nM, IBTX 690 +/- 96 nM) and SR-141716A. The data suggest that activation of the CaR in the PvN network by Ca(2+) leads to synthesis and/or release of metabolites of the CYP epoxygenase pathway and metabolism of DAG to 2-AG and subsequently to GEETs. The findings indicate a role for 2-AG and its metabolites in Ca(2+)-induced relaxation of resistance arteries; therefore this receptor may be a potential target for the development of new vasodilator compounds for antihypertensive therapy.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Arachidonic Acids; Calcium; Cytochrome P-450 Enzyme Inhibitors; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Endocannabinoids; Enzyme Inhibitors; Glycerides; Lipoprotein Lipase; Male; Mesenteric Arteries; Miconazole; Peptides; Phenylephrine; Phospholipase A2 Inhibitors; Phospholipases A2; Piperidines; Potassium Channel Blockers; Potassium Channels, Calcium-Activated; Pyrazoles; Quinacrine; Rats; Rats, Wistar; Receptor, Cannabinoid, CB1; Receptors, Calcium-Sensing; Rimonabant; Signal Transduction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

Acetylcholine caused an endothelium-dependent relaxation in isolated rabbit mesenteric small artery in the presence of nitro L-arginine and indomethacin. The acetylcholine-induced relaxation was attenuated by high K(+) solution, suggesting that the response is mediated by a membrane potential-sensitive mechanism, presumably an endothelium-derived hyperpolarizing factor. The acetylcholine-induced relaxation was also inhibited with tetraethylammonium, 4-aminopyridine and charybdotoxin, but not with Ba(2+), apamin, iberiotoxin nor glibenclamide. The relaxation was abolished by a combination of apamin and charybdotoxin, but iberiotoxin could not replace charybdotoxin in this combination. The responses to charybdotoxin and 4-aminopyridine were synergistic but neither apamin nor iberiotoxin increased the effect of 4-aminopyridine. Clotrimazole and proadifen inhibited the acetylcholine-induced relaxation, but these drugs also inhibited the cromakalim-induced relaxation, while protoporphyrin IX inhibited the acetylcholine- but not cromakalim-induced relaxation. 17-Octadecynoic acid and 1-aminobenzotriazole did not affect the response to acetylcholine. Four regioisomers of epoxyeicosatrienoic acids did not relax endothelium-denuded artery. A gap junction inhibitor 18alpha-glycyrrhetinic acid attenuated the relaxation to acetylcholine. It is suggested that in rabbit mesenteric artery, the acetylcholine-induced, nitric oxide- and prostacyclin-independent relaxation is mainly mediated by 4-aminopyridine- and charybdotoxin-sensitive K(+) channels and that the relaxation is not mediated through cytochrome P450 enzyme metabolites. The contribution of heterocellular gap junctional communication to the relaxation is discussed.

Topics: 8,11,14-Eicosatrienoic Acid; Acetylcholine; Animals; Arachidonic Acids; Cromakalim; Cytochrome P-450 Enzyme Inhibitors; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Glycyrrhetinic Acid; Male; Mesenteric Arteries; Muscle Relaxation; Muscle, Smooth, Vascular; Nitroprusside; Norepinephrine; Potassium Channel Blockers; Potassium Chloride; Rabbits; Tetraethylammonium; Vasoconstrictor Agents; Vasodilator Agents