title: Pre-contraction with the thromboxane-mimetic U46619 enhances P2X receptor-mediated contractions in isolated porcine splenic artery.
abstract: We have previously demonstrated that the thromboxane-mimetic U46619 enhances α(2)-adrenoceptor-mediated contractions through increased activation of extracellular signal-regulated kinase (ERK). In this study, we determined whether U46619 also enhances P2X-mediated contractions through the same pathway. Segments of porcine splenic artery were mounted in isolated tissue baths. Tissues were pre-contracted with U46619 to 10-20% of the response to 60 mM KCl prior to addition of α,β-methylene ATP (P2X receptor agonist). The effect of inhibition of ERK activation with the mitogen-activated protein (MAP)/ERK kinase inhibitor PD98059 (50 μM), Rho kinase inhibition with Y27632 (10 μM), p38 MAP kinase with SB203580 (10 μM) or L-type calcium channels with nifedipine (1 μM) on both the direct and enhanced contractions was then determined. U46619 enhanced the contractions to α,β-methylene ATP. Although PD98059 inhibited the direct contractions to α,β-methylene ATP, it had no effect on the U46619-enhanced contractions. Similarly, Y27632 and SB203580 inhibited the direct contractions to α,β-methylene ATP, but had no effect on the enhanced contractions. Nifedipine inhibited the responses to α,β-methylene ATP in the absence and presence of U46619. This study demonstrates that pre-contraction with U46619 enhances P2X-mediated contractions in the porcine splenic artery through a mechanism independent of ERK, Rho kinase and p38 MAP kinase. Further studies are required to determine the exact mechanism involved.
authors: School of Biomedical Sciences, Queen's Medical Centre, University of Nottingham, Medical School, Nottingham, UK. richard.roberts@nottingham.ac.uk
authors: R E
authors: RE
authors: Roberts
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology*; D000818:Animals; D018716:Molecular Mimicry; D009924:Organ Culture Techniques; D058469:Receptors, Purinergic P2X / Q000502:physiology*; D013157:Splenic Artery / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013931:Thromboxanes / Q000494:pharmacology* / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D058469:Receptors, Purinergic P2X; D013931:Thromboxanes; D014662:Vasoconstrictor Agents; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid