Ferric iron and cobalt (III) compounds to safely decrease hydrogen sulfide in the body?

To sort out the putative roles of endogenous hydrogen sulfide (H ₂S) in clinical conditions wherein systemic inflammation or hypoxia is present, it becomes crucial to develop approaches capable of affecting H ₂S concentration that can be safely applied in humans. We have investigated a paradigm, which could achieve such a goal, using vitamin B12 (vit.B12), at the dose recommended in cyanide poisoning, and very low levels of methemoglobin (MetHb). Hydroxocobalamin in the plasma, supernatant of kidney, and heart tissue homogenates of rats that had received vit.B12 (140 mg.kg ^-1 intravenous) was found in the μM range. Exogenous H ₂S (100 μM) added to the plasma or supernatants of these rats decreased at a significantly higher rate than in control rats. In the latter however a spontaneous oxidation of exogenous H₂S occurred. In vitro, hydroxocobalamin solution (100 μM) decreased, within <2 min, an equimolar concentration of H₂S by 80%. Three to five percent MetHb prevented H₂S induced hyperventilation in vivo and decreased exogenous H ₂S in vitro by 25-40 μM within 30 s. Our observations lead to the hypothesis that innocuous levels of MetHb and vit.B12 could be a used as an effective and safe way to test the role of endogenous H₂S in vivo. Antioxid. Redox Signal. 19, 510-516.