[Modulation of respiratory activity of renal macrophages in sea bass (Dicentrarchus labrax) by chronic exposure to sublethal concentration of ammonia].

Sea bass (Dicentrarchus labrax) were exposed for 71 days to three different ammonia concentrations corresponding to 0, 15 and 25% of the lethal threshold concentration causing the death of half a fish population in 96 hours. The study of the respiratory burst from sea bass renal macrophages showed that the luminol dependent chemiluminescence (CL) emitted following stimulation with mezerein is higher when fishes were previously exposed to ammonia. Therefore, it seemed that chronically exposure of fishes to sublethal concentrations of ammonia primed their renal macrophages to secrete higher amounts of oxygen activated species during respiratory burst, even several days after the transfer of fishes into a standard environment. The stimulated-macrophage CL was partially inhibited by sodium azide, superoxide dismutase and a nitric oxide-synthesis inhibitor, the N5-(-1-iminoethyl)-L-ornithine monochloride, showing that hydrogen peroxide, superoxide anions and nitric oxide were released by renal macrophages from sea bass during the respiratory burst. These reactive species could react together to generate peroxynitrite, a strong bactericidal agent.