GILL DIFFUSION AS A PHYSIOLOGICAL MECHANISM FOR HYDROGEN-PEROXIDE ELIMINATION BY FISH

Hydrogen peroxide is metabolized by the specific enzymatic action of c atalase and glutathione peroxidase in animal tissues. The relatively l ow catalase and glutathione peroxidase activities found in the blood o f fish may be related to the ability of gills to eliminate hydrogen pe roxide into the aquatic environment. Poecilia vellifera releases hydro gen peroxide apparently by gill diffusion into the environment, result ing in a steady-state H2O2 concentration of about 0.6 mu M in the surr ounding water. This physiological mechanism resembles ammonia excretio n by teleost fish.