In Isolated Vessels H2s Is A Less Effective Scavenger Of Exogenous Superoxide Than Sod

Recent studies suggest that hydrogen sulfide (H 2 S) exhibits potent antioxidant capacity and improves vascular and tissue functions in oxidative stress conditions. Thus we aimed to compare the direct antioxidant efficacy of H 2 S and superoxide dismutase (SOD). Isometric force of isolated rat carotid arteries and gracilis veins was measured with a wire myograph. The vasomotor effect of the superoxide‐generator pyrogallol (10 −5 M) was obtained in control conditions, and then in the presence of SOD (120 U/ml) or H 2 S (10 −5 M or 10 −4 M), respectively. Spectrophotometric measurements were performed to detect the effect of SOD and H 2 S on the auto‐oxidation of pyrogallol to superoxide Pyrogallol increased the isometric force of carotid arteries (9.7±0.8mN), which was abolished by SOD (5.3±0.8mN), but was not affected by 10 −5 M H 2 S (9.1±0.5mN), whereas 10 −4 M H 2 S significantly reduced it (8.1±0.7mN). Pyrogallol significantly increased the isometric force of gracilis veins (1.3±0.2mN), which was abolished by SOD (0.9±0.2mN), whereas 10 −5 M (1.3±0.2mN) or 10 −4 M H 2 S (1.2±0.2mN) did not significantly affect it. Pyrogallol‐induced superoxide production was measured by a spectrophotometer (A 420 =0.19±0.0). SOD reduced absorbance (A 420 =0.02±0.0), but 10 −5 M H 2 S did not (A 420 =0.18±0.0), whereas 10 −4 M H 2 S slightly, but significantly reduced it (A 420 =0.15±0.0). This in vitro vascular bioassay study suggests that the superoxide scavenging efficacy of H 2 S is substantially less than that of SOD, suggesting that the beneficial effects of H 2 S on vascular function in conditions of oxidative stress could be due primarily to secondary mechanisms activated by H 2 S.