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In mature spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), acetylcholine and the calcium ionophore A-23187 release endothelium-derived contracting factors (EDCFs), cyclooxygenase derivatives that activate thromboxane-endoperoxide (TP) receptors on vascular smooth muscle. The EDCFs released by acetylcholine are most likely prostacyclin and prostaglandin (PG)H2, whereas those released by A-23187 remain to be identified. Isometric tension and the release of PGs were measured in rings of isolated aortas of WKY and SHR. A-23187 evoked the endothelium-dependent release of prostacyclin, thromboxane A2, PGF2α, PGE2, and possibly PGH2 (PGI2 ⪢ thromboxane A2 = PGF2α = PGE2). In SHR aortas, the release of prostacyclin and thromboxane A2 was significantly larger in response to A-23187 than to acetyicholine. In response to the calcium ionophore, the release of thromboxane A2 was significantly larger in aortas of SHR than in those of WKY. In both strains of rat, the inhibition of cyclooxygenase-1 prevented the release of PGs and the occurrence of endothelium-dependent contractions. Dazoxiben, the thromboxane synthase inhibitor, abolished the A-23187-dependent production of thromboxane A2 and inhibited by approximately one-half the endothelium-dependent contractions. U-S 1605, an inhibitor of PGI synthase, reduced the release of prostacyclin elicited by A-23187 but induced a parallel increase in the production of PGE2 and PGF2α, suggestive of a PGH2 spillover, which was associated with the enhancement of the endothelium-dependent contractions. These results indicate that in the aorta of SHR and WKY, the endothelium-dependent contractions elicited by A-23187 involve the release of thromboxane A2 and prostacyclin with a most likely concomitant contribution of PGH2. [ABSTRACT FROM AUTHOR]

Background and Purpose: The purpose of the present study was to determine whether a stimulator of soluble guanylyl cyclase, BAY 41-2272, inhibits platelet aggregation and to clarify its interaction with nitric oxide (NO)., Experimental Approach: Blood was collected from anaesthetized Wistar Kyoto rats. The aggregation of washed platelets was measured and the production of cAMP and cGMP was determined., Key Results: In adenosine 5'-diphosphate (ADP)-induced platelet aggregation, the anti-aggregating effects of BAY 41-2272, nitroglycerin, sodium nitroprusside and DEA-NONOate were associated with increased levels of cGMP while that of beraprost, a prostacyclin analogue, was correlated with an increase in cAMP. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) prevented the effects of BAY 41-2272 and that of nitroglycerin and sodium nitroprusside, but only inhibited the increase in cGMP produced by of DEA-NONOate. Hydroxocobalamin, an NO scavenger, inhibited the effects of the three NO donors and BAY 41-2272 but did not affect those of beraprost. ADP-induced aggregation and the effects of BAY 41-2272 were not affected by L-nitroarginine. A positive interaction was observed between BAY 41-2272 and the three NO donors. BAY 41-2272 potentiated also the anti-aggregating effects of beraprost, and again this potentiation was inhibited by hydroxocobalamin., Conclusions and Implications: Inhibition of platelet aggregation by BAY 41-2272 requires the reduced form of soluble guanylyl cyclase and the presence of NO. The positive interaction observed between BAY 41-2272 and various NO donors is qualitatively similar whatever the mechanism involved in NO release. Furthermore, a potent synergism is observed between BAY 41-2272 and a prostacyclin analogue, but only in the presence of NO., (© 2010 The Authors. British Journal of Pharmacology © 2010 The British Pharmacological Society.)

Human saphenous veins (SV) are used for coronary bypass surgery despite the higher rate of graft failure observed as compared to arteries. A higher production of reactive oxygen species (ROS) in SV than in internal mammary artery (IMA) has been incriminated as possibly implicated in graft failure. NADPH oxidase, involved in vascular ROS production, was therefore characterized in human smooth muscle cells from SV. ROS production was confirmed to be essentially NADPH oxidase dependent in cultured smooth muscle cells (SMC) from human SV and increased in comparison with IMA. To investigate the role of NADPH oxidase subunits, siRNA for nox1, nox2, or p47 mRNA were studied. In cultured venous SMC under unstimulated conditions, inhibition of nox1 or nox2 mRNA decreased ROS production, whereas p47 silencing increased it. During angiotensin II (AngII) activation, nox2 or p47 mRNA silencing decreased ROS production, while nox1 inhibition had no effect. Venous SMC express functional nox1 and nox2. Only nox2 is implicated in response to AngII whilst nox1 is involved in unstimulated ROS production. p47 negatively regulates ROS generation under basal conditions, whereas it enhances AngII increased ROS production. Thus, nox1, nox2, and p47 have distinct roles in NADPH oxidase activity in human veins.

In mature spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), acetylcholine and the calcium ionophore A-23187 release endothelium-derived contracting factors (EDCFs), cyclooxygenase derivatives that activate thromboxane-endoperoxide (TP) receptors on vascular smooth muscle. The EDCFs released by acetylcholine are most likely prostacyclin and prostaglandin (PG)H(2), whereas those released by A-23187 remain to be identified. Isometric tension and the release of PGs were measured in rings of isolated aortas of WKY and SHR. A-23187 evoked the endothelium-dependent release of prostacyclin, thromboxane A(2), PGF(2alpha), PGE(2), and possibly PGH(2) (PGI(2) >> thromboxane A(2) = PGF(2alpha) = PGE(2)). In SHR aortas, the release of prostacyclin and thromboxane A(2) was significantly larger in response to A-23187 than to acetylcholine. In response to the calcium ionophore, the release of thromboxane A(2) was significantly larger in aortas of SHR than in those of WKY. In both strains of rat, the inhibition of cyclooxygenase-1 prevented the release of PGs and the occurrence of endothelium-dependent contractions. Dazoxiben, the thromboxane synthase inhibitor, abolished the A-23187-dependent production of thromboxane A(2) and inhibited by approximately one-half the endothelium-dependent contractions. U-51605, an inhibitor of PGI synthase, reduced the release of prostacyclin elicited by A-23187 but induced a parallel increase in the production of PGE(2) and PGF(2alpha), suggestive of a PGH(2) spillover, which was associated with the enhancement of the endothelium-dependent contractions. These results indicate that in the aorta of SHR and WKY, the endothelium-dependent contractions elicited by A-23187 involve the release of thromboxane A(2) and prostacyclin with a most likely concomitant contribution of PGH(2).