A dose / response study with 2,3,7,8 - TCDD in the rainbow trout: Onchorhynchus mykiss

A dose / response study was carried out with Rainbow trout. Three, six and twelve weeks after a single i.p. injection of circa 0.01, 0.05, 0.1, 0.5, 1.0 and 5.0 μg/kg, biochemical as well as toxicological effects were monitored. Liver weight increase and the first signs of growth inhibition occurred respectively six and eleven weeks after a dosage of 5 μg/kg. Inconsistent effects on relative spleen weight were found, probably as a combined result of the microscopically observed congestion and lymphoid atrophy. The increase in EROD activity in the liver was dose-related. Both EROD induction in the liver and histopathological changes in the spleen were observed at a dose as low as circa 0.5 μg/kg.