Abstract
The mechanisms of relaxation to nitric oxide (NO)-independent soluble guanylyl cyclase (sGC) activator BAY 41-2272 [5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4-ylamine] were investigated in isolated ovine pulmonary artery. BAY 41-2272 (1 nM-10 μM) produced concentration-dependent relaxation of endothelium-denuded pulmonary artery rings (pD2 = 6.82 ± 0.16; Emax = 92.30 ± 2.31%; n = 8), precontracted with 1 μM 5-hydroxytryptamine (serotonin). 1-H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one (ODQ; 10 μM), an inhibitor of sGC, partially inhibited (Emax = 57.10 ± 3.10%; n = 6) the relaxation response of BAY 41-2272. In comparison with ODQ, sodium pump inhibitor ouabain (1 μM) produced a greater decrease in the vasodilator response of BAY 41-2272 (Emax = 20.17 ± 4.55%; n = 6). K+-free solution also attenuated (Emax = 39.97 ± 3.52%; n = 6) BAY 41-2272-induced relaxation. ODQ (10 μM) plus 1 μM ouabain abolished the relaxant response of BAY 41-2272 (Emax = 12.09 ± 3.76%, n = 6 versus vehicle control dimethyl sulfoxide; Emax = 15.83 ± 1.72%, n = 6). KT-5823 [1-oxo-9.12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-I][1,6]benzodiazocine-10-carboxylic acid methyl ester (2 μM), a specific inhibitor of protein kinase G had no effect on 10 μM ODQ-insensitive relaxation evoked by BAY 41-2272. BAY 41-2272 (10 μM) inhibited Ca2+-induced contractions in K+-depolarized preparations. BAY 41-2272 (10 μM) caused about a 14-fold increase in the intracellular cGMP over the basal level, which was completely inhibited by 10 μM ODQ. BAY 41-2272 (0.1, 1.0, and 10 μM) significantly (P < 0.05) increased ouabain-sensitive 86Rb uptake in a concentration-dependent manner. BAY 41-2272 (10 μM) also stimulated sarcolemmal Na+-K+-ATPase activity. However, 10 μM ODQ had no significant effect on either basal or BAY 41-2272-stimulated 86Rb uptake/Na+-K+-ATPase activities. In conclusion, this study provides the first evidence of sodium pump stimulation by BAY 41-2272 independent of cGMP as an additional mechanism to sGC activation in relaxation of ovine pulmonary artery.
Footnotes
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.083824.
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ABBREVIATIONS: sGC, soluble guanylate cyclase; BAY 41-2272, 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4-ylamine; PSS, physiological saline solution; 5-HT, 5-hydroxytryptamine (serotonin); ACh, acetylcholine; ODQ, 1-H-[1,2,4]oxadiazole[4,3-a]quinoxaline-1-one; KT-5823, [1-oxo-9.12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-I][1,6]benzodiazocine-10-carboxylic acid methyl ester; KT-5720, (9S, 10R, 12R)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-i][1,6]benzodiazocine-10-carboxylic acid hexyl ester; Pi, inorganic phosphate; DMSO, dimethyl sulfoxide; 8-Br-cGMP, 8-bromo-cGMP; ANOVA, analysis of variance; YC-1, 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole; PDE5, phosphodiesterase-5; PKA, protein kinase A.
- Received January 16, 2005.
- Accepted March 23, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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