| 19406003 |
Alda JO, Valero MS, Pereboom D, Gros P, Garay RP: Endothelium-independent vasorelaxation by the selective alpha estrogen receptor agonist propyl pyrazole triol in rat aortic smooth muscle. J Pharm Pharmacol. 2009 May;61(5):641-6.
OBJECTIVES: This study investigated the signalling mechanism of the relaxant responses to the estrogen receptor (ERalpha) agonist PPT (propyl pyrazole triol) in endothelium-denuded rat aortic rings. METHODS: Several compounds, including protein kinase G (PKG) inhibitors and potassium channel inhibitors, were tested against PPT-dependent rat aortic relaxation. Cyclic GMP and cytosolic calcium responses to PPT in isolated aortic smooth muscle were investigated in parallel. KEY FINDINGS: PPT vasorelaxation was largely reduced by the selective ERalpha antagonist methyl-piperidinopyrazole (MPP; -91.6+/-2.5%), by the selective PKG inhibitor Rp-8-Br-cGMP (-78.6+/-4.9%), by the specific soluble guanylyl cyclase inhibitor ODQ (1H-(1,2,4)-oxadiazolo [4,3-a] quinoxalin-1-one; -85.3+/-5.2%) and to a lesser extent by the selective BKCa (large-conductance calcium- and voltage-activated potassium channel) inhibitor iberiotoxin (-59.3%), the selective IKCa (intermediate-conductance calcium-activated potassium channel) inhibitor TRAM-34 (1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole; -50.7%) and the voltage-gated potassium channel inhibitor 4-aminopyridine (-40.8%). In isolated aortic smooth muscle, PPT strongly enhanced the cyclic GMP content (+144%) and Rp-8-Br-cGMP largely reduced the PPT-dependent calcium signal (-80.8%). CONCLUSIONS: ERalpha receptor stimulation in rat aortic smooth muscle evokes a PKG-signalling pathway, likely triggering relaxation by BKCa and IKCa channel opening. |
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