Gill diffusion as a physiological mechanism for hydrogen peroxide elimination by fish.

Hydrogen peroxide is metabolized by the specific enzymatic action of catalase and glutathione peroxidase in animal tissues. The relatively low catalase and glutathione peroxidase activities found in the blood of fish may be related to the ability of gills to eliminate hydrogen peroxide into the aquatic environment. Poecilia vellifera releases hydrogen peroxide apparently by gill diffusion into the environment, resulting in a steady-state H2O2 concentration of about 0.6 microM in the surrounding water. This physiological mechanism resembles ammonia excretion by teleost fish.