Abstract
The production of reactive oxygen species, including hydrogen peroxide (H2O2), is increased in diseased blood vessels. Although H2O2 leads to impairment of the nitric oxide (NO)/soluble guanylate cyclase (sGC)/cGMP signaling pathway, it is not clear whether this reactive molecule affects the redox state of sGC, a key determinant of NO bioavailability. To clarify this issue, mechanical responses of endothelium-denuded rat external iliac arteries to BAY 41-2272 (sGC stimulator), BAY 60-2770 (sGC activator), nitroglycerin (NO donor), acidified NaNO2 (exogenous NO) and 8-Br-cGMP (cGMP analog) were studied under exposure to H2O2. The relaxant response to BAY 41-2272 (pD2: 6.79 ± 0.10 and 6.62 ± 0.17), BAY 60-2770 (pD2: 9.57 ± 0.06 and 9.34 ± 0.15) or 8-Br-cGMP (pD2: 5.19 ± 0.06 and 5.24 ± 0.08) was not apparently affected by exposure to H2O2. In addition, vascular cGMP production stimulated with BAY 41-2272 or BAY 60-2770 in the presence of H2O2 was identical to that in its absence. On the other hand, nitroglycerin-induced relaxation was markedly attenuated by exposing the arteries to H2O2 (pD2: 8.73 ± 0.05 and 8.30 ± 0.05), which was normalized in the presence of catalase (pD2: 8.59 ± 0.05). Likewise, H2O2 exposure impaired the relaxant response to acidified NaNO2 (pD2: 6.52 ± 0.17 and 6.09 ± 0.16). These findings suggest that H2O2 interferes with the NO-mediated action, but the sGC redox equilibrium and the downstream target(s) of cGMP are unlikely to be affected in the vasculature.
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