thromboxane-a2 and manoalide

We investigated whether or not acetylcholine elicited an endothelium-dependent contraction and whether an arachidonic acid metabolite was involved in the acetylcholine-induced contraction in ring preparations of rat renal arteries. Acetylcholine (0.1-100 microM) caused a transient contraction in endothelium-intact arteries in a concentration-dependent manner. The contraction induced by acetylcholine (10 microM) was enhanced by pretreatment with NG-nitro-L-arginine (100 microM), a nitric oxide synthase inhibitor, and was abolished by mechanical removal of the endothelium. Atropine (0.1 microM), quinacrine (1 and 3 microM), manoalide (0.1 and 1 microM), aspirin (1 and 10 microM), indomethacin (30 and 300 nM), ONO-3708 (9,11-dimethyl-methane-11,12-methano-13,14-dihydro-13-aza-14- oxo-15(beta)-cyclophenyl-omega-pentenor-thromboxane A2 L-arginine salt) (10 nM), S-1452 (calcium (5Z)-1R,2S,3S,4S-7-[3-phenylsulphonyl-aminobicyclo[2.2.1]hep t-2yl]-5- heptenoate hydrate) (3 nM) and SQ29,548 ([1S- [1 alpha,2 beta(5Z),3 beta,4 alpha]]-7-[3-[[2-[(phenylamino) carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoi++ + c acid) (3 and 10 nM), but not hexamethonium (1 microM), OKY-046 (sodium (E)-3-[4-(1- imidazolylmethyl)phenyl]-2-propenoic acid hydrochloride monohydrate) (100 microM) and CS-518 (sodium 2-(1-imidazolylmethyl)-4,5- dihydrobenzo[b]thiophene-6-carboxylate) (10 microM) significantly attenuated the acetylcholine (10 microM)-induced endothelium-dependent contractions in renal arteries pretreated with NG-nitro-L-arginine. These findings suggest that acetylcholine causes endothelium-dependent contraction by stimulation of muscarinic receptors in rat renal arteries, and that an arachidonic acid metabolite(s) of the cyclooxygenase pathway is involved in this endothelium-dependent contraction.

Topics: Acetylcholine; Animals; Arachidonic Acid; Arginine; Aspirin; Atropine; Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Dose-Response Relationship, Drug; Endothelium, Vascular; Fatty Acids, Monounsaturated; Fatty Acids, Unsaturated; Hexamethonium; Hydrazines; Male; Muscle Contraction; Muscle, Smooth, Vascular; Nitroarginine; Phospholipases A; Quinacrine; Rats; Rats, Inbred WKY; Receptors, Prostaglandin; Renal Artery; Terpenes; Thromboxane A2; Thromboxane-A Synthase

The effects of the stable analogue of TxA2, U46619, on polymorphonuclear leukocyte (PMN) function were investigated. U46619, at micromolar concentrations, inhibited fMLP-stimulated aggregation, beta-glucuronidase release, and superoxide production. fMLP-induced LTB4 synthesis was also inhibited. U46619 did not modify intracellular Ca2+ increase induced by fMLP in Fura-2-loaded PMN, suggesting that early events of cell activation were not involved. In fact, U46619 also inhibited aggregation, beta-glucuronidase release, superoxide anion and LTB4 production induced by the calcium ionophore A23187. By comparison with the specific 5-lipoxygenase inhibitor, L-663,536, which prevented LTB4 synthesis without affecting degranulation, we excluded the impairment of PMN function by U46619 as a consequence of the reduction of this endogenous agonist. TLC separation of lipid extracts from [3H]-AA-loaded PMN, stimulated by A23187, showed significant reduction of the radioactivity associated with authentic free AA, suggesting that U46619 could interfere with mechanisms regulating AA release from membrane phospholipids. This suggestion is also supported by the observation that manoalide, a standard inhibitor of phospholipase A2, similarly to U46619, inhibits beta-glucuronidase release from stimulated PMN. Prostaglandin endoperoxides, produced by cells participating in inflammatory reactions, might therefore play a role in modulating PMN activities.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Calcimycin; Cell Adhesion; Fura-2; Humans; Indoles; Leukotriene Antagonists; Leukotriene B4; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Phospholipases A; Phospholipases A2; Prostaglandin Endoperoxides, Synthetic; Superoxides; Terpenes; Thromboxane A2; Vasoconstrictor Agents