Impact of nitrite exposure on endocrine, osmoregulatory and cytoprotective functions in the marine teleost Sparus sarba.

The effects of nitrite, at varying concentrations (0, 25 and 50mg/l), on silver sea bream (Sparus sarba), was assessed after 7 days exposure. Nitrite exposure resulted in an elevated renosomatic index in parallel with increased kidney water content. Measurements of serum thyroid hormones demonstrated that levels of thyroxine (T(4)) were decreased upon nitrite exposure whereas triiodothyronine (T(3)) concentrations remained unchanged. Nitrite did not affect serum K and Na levels but did cause an increase in gill sodium pump (Na(+)-K(+)-ATPase) activity. Using immunoassays, it was found that the abundance of the water channel protein, aquaporin 3 (AQP3) was unchanged in gills but decreased in kidneys of sea bream upon nitrite exposure. Immunoassay analysis also demonstrated that the amount of the heat shock protein 70 (HSP70) family were increased in gills, kidney and liver during nitrite exposure whereas amounts of the heat shock protein 90 (HSP90) family increased in kidneys and liver. Taken together, the findings from this study provide new insights into how nitrite affects osmoregulatory, endocrine processes and heat shock protein expression in a marine fish.