Molecular mechanisms underlying rat mesenteric artery vasorelaxation induced by the nitric oxide-independent soluble guanylyl cyclase stimulators BAY 41-2272 [5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl] pyrimidin-4-ylamine] and YC-1 [3-(5′-hydroxymethyl-2′-furyl)-1- benzyl indazole]

The aim of this study was to investigate the mechanisms of relaxation to the nitric oxide (NO)-independent soluble guanylyl cyclase (sGC) stimulators 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl] pyrimidin-4-ylamine (BAY 41-2272) and 3-(5′-hydroxymethyl-2′-furyl)- 1-benzyl indazole (YC-1) in the rat mesenteric artery. In endothelium-intact rings, BAY 41-2272 (0.0001-1 μM) and YC-1 (0.001-30 μM) caused concentration-dependent relaxations (pEC₅₀ values of 8.21 ± 0.05 and 6.75 ± 0.06, respectively), which were shifted to the right by 6-fold in denuded rings. The sGC inhibitor H-[1,2,4]oxadiazolo [4,3,-a]quinoxalin-1-one (ODQ) (10 μM) partially attenuated the maximal responses to BAY 41-2272 and YC-1 and displaced their curves to the right by 9- to 10-fold in intact and 3-fold in denuded vessels. The NO synthesis inhibitor N^ω-nitro-L-arginine methyl ester (100 μM) and the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (100 μM) reduced BAY 41-2272 and YC-1 relaxations, whereas the phosphodiesterase type 5 inhibitor sildenafil (0.1 μM) potentiated these responses. The phosphatase inhibitor calyculin A (50 nM) reduced the relaxant responses, and high concentrations of BAY 41-2272 (1 μM) and YC-1 (10 μM) inhibited Ca²⁺-induced contractions in K⁺-depolarized rings. BAY 41-2272 (0.1 μM) and YC-1 (1 μM) markedly elevated cGMP levels in an ODQ-sensitive manner. Coincubation of BAY 41-2272 or YC-1 with a NO donor resulted in a synergistic inhibition of phenylephrine-induced contractions paralleled by marked increases in cGMP levels. In conclusion, BAY 41-2272 and YC-1 relax the mesenteric artery through cGMP-dependent and -independent mechanisms, including blockade of Ca²⁺ influx. The synergistic responses probably reflect the direct effects of NO and NO-independent sGC stimulators on the enzyme, thus representing a potential therapeutic effect by permitting reductions of nitrovasodilator dose.