BAY 41-2272 [5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4-yl]ylamine]-induced dilation in ovine pulmonary artery:: Role of sodium pump

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-3yl]-pyrimidin-4-ylamine] were investigated in isolated ovine pulmonary artery. BAY 41-2272 (1 nM - 10 mu M) produced concentration-dependent relaxation of endothelium-denuded pulmonary artery rings (pD(2) = 6.82 +/- 0.16; E-max = 92.30 +/- 2.31%; n = 8), precontracted with 1 mu M 5-hydroxytryptamine (serotonin). 1-H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one (ODQ; 10 mu M), an inhibitor of sGC, partially inhibited (E-max = 57.10 +/- 3.10%; n = 6) the relaxation response of BAY 41-2272. In comparison with ODQ, sodium pump inhibitor ouabain ( 1 mu M) produced a greater decrease in the vasodilator response of BAY 41-2272 (E-max = 20.17 +/- 4.55%; n = 6). K+-free solution also attenuated (E-max = 39.97 +/- 3.52%; n = 6) BAY 41-2272-induced relaxation. ODQ (10 mu M) plus 1 mu M ouabain abolished the relaxant response of BAY 41-2272 (E-max = 12.09 +/- 3.76%, n = 6 versus vehicle control dimethyl sulfoxide; E-max = 15.83 +/- 1.72%, n = 6). KT-5823 [1-oxo-9.12-epoxy-1H-diindolo][1,2,3fg:3 ',2 ',1 '-kl] pyrrolo[3,4-l][1,6]benzodiazocine-10-carboxylic acid methyl ester (2 mu M), a specific inhibitor of protein kinase G had no effect on 10 mu M ODQ-insensitive relaxation evoked by BAY 41-2272. BAY 41-2272 (10 mu M) inhibited Ca2+-induced contractions in K+-depolarized preparations. BAY 41-2272 (10 mu M) caused about a 14-fold increase in the intracellular cGMP over the basal level, which was completely inhibited by 10 mu M ODQ. BAY 41-2272 (0.1, 1.0, and 10 mu M) significantly (P < 0.05) increased ouabain-sensitive Rb-86 uptake in a concentration-dependent manner. BAY 41-2272 (10 mu M) also stimulated sarcolemmal Na+-K+-ATPase activity. However, 10 mu M ODQ had no significant effect on either basal or BAY 41-2272-stimulated Rb-86 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.