UC Davis

Hydrogen Sulfide (H2S) is a colorless, flammable, water-soluble, rotten egg-smelling gas placed on Homeland Security’s chemicals of concern list. Exposure to H2S can be either intentional or accidental. Some accidental exposures include industrial accidents such as petroleum refinery malfunction, or natural exposures such as volcanic emissions. Intentional exposures may occur as in suicide or terrorism. This study aims to test the hypothesis that inhibition of cytochrome C oxidase (COX) activity can be used to diagnose acute H2S poisoning. To do this, we examined various tissues from mice including blood platelets, and select brain regions, and cardiac and skeletal muscles. Mice were exposed to 1000ppm of H2S for 15, 30, or 60 minutes. The blood and tissues from each group were collected immediately after exposure following euthanasia by decapitation. The blood platelets were isolated and analyzed immediately after collection. The tissues were stored at -80C until they were analyzed. The COX activity was measured spectrophotometrically in both the platelets and tissues using a Complex IV Rodent Enzyme Microplate Assay Kit. COX activity in the brain varied by region, with the cortex being the most sensitive and most inhibited at 60 minutes and the cerebellum the least inhibited. We determined that the COX activity in the heart muscle was not significantly affected by H2S poisoning. The diaphragm was more sensitive than the heart muscle, with maximum inhibition observed at thirty minutes following H2S exposure at 1000 ppm.