In isolated vessels H2S is a less effective scavenger of exogenous superoxide than SOD

Abstract

Recent studies suggest that hydrogen sulfide (H2S) exhibits potent antioxidant capacity and improves vascular and tissue functions in oxidative stress conditions. Thus we aimed to compare the direct antioxidant efficacy of H2S 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 (10−5M) was obtained in control conditions, and then in the presence of SOD (120 U/ml) or H2S (10−5M or 10−4M), respectively. Spectrophotometric measurements were performed to detect the effect of SOD and H2S on the auto‐oxidation of pyrogallol to superoxidePyrogallol 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 10−5M H2S (9.1±0.5mN), whereas 10−4M H2S 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 10−5M (1.3±0.2mN) or 10−4M H2S (1.2±0.2mN) did not significantly affect it. Pyrogallol‐induced superoxide production was measured by a spectrophotometer (A420=0.19±0.0). SOD reduced absorbance (A420=0.02±0.0), but 10−5M H2S did not (A420=0.18±0.0), whereas 10−4M H2S slightly, but significantly reduced it (A420=0.15±0.0).This in vitro vascular bioassay study suggests that the superoxide scavenging efficacy of H2S is substantially less than that of SOD, suggesting that the beneficial effects of H2S on vascular function in conditions of oxidative stress could be due primarily to secondary mechanisms activated by H2S.