title: Hydrogen sulfide oxidation and the arterial chemoreflex: effect of methemoglobin.
abstract: Endogenous H(2)S has been proposed to transduce the effects of hypoxia in the carotid bodies (CB). To test this hypothesis, we created a sink for endogenously produced H(2)S by inducing ∼10% methemoglobinemia via the injection of 250 mg of sodium nitrite in spontaneously breathing anaesthetized sheep. Methemoglobinemia has been shown to catalyze the oxidation of large quantities of sulfide in the blood and tissues. We found that the presence of metHb completely abolished the ventilatory stimulation induced by 10 mg NaHS (i.v.), which in control conditions mimicked the effects of breathing 6-7 tidal volumes of nitrogen, confirming the dramatic increase in the oxidative power of the blood for sulfide. The ventilatory responses to hypoxia (10% O(2)), nitrogen and hyperoxia were in no way depressed by the metHb. Our results demonstrate that the ventilatory chemoreflex is not depressed in the presence of a high oxidative capacity for sulfide and challenge the view that H(2)S transduces the effects of hypoxia in the CB.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Medicine, Pennsylvania State University, College of Medicine, Penn State Milton Hershey Medical Centre, Hershey, PA, USA. phaouzi@hmc.psu.edu
authors.forename: Philippe
authors.initials: P
authors.lastname: Haouzi
authors.forename: Harold
authors.initials: H
authors.lastname: Bell
authors.forename: Maeve
authors.initials: M
authors.lastname: Philmon
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D002339:Carotid Arteries / Q000187:drug effects*; D006862:Hydrogen Sulfide / Q000494:pharmacology*; D018496:Hyperoxia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D008706:Methemoglobin / Q000494:pharmacology*; D008954:Models, Biological; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D011029:Pneumoradiography; D012018:Reflex / Q000187:drug effects*; D012756:Sheep; D012977:Sodium Nitrite / Q000494:pharmacology; D013440:Sulfides / Q000097:blood; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D013440:Sulfides; D008706:Methemoglobin; D012977:Sodium Nitrite; D009584:Nitrogen; D006862:Hydrogen Sulfide