Toxicology of dietary uranium in lake whitefish (Coregonus clupeaformis)

Using responses ranging from whole animal to the molecular level, the toxicological significance of the accumulation and distribution of uranium (U) in adult lake whitefish fed a commercial diet contaminated with three concentrations of U, 100, 1000 and 10000 µg U/g, for 10, 30, and 100 days, as described in the previous manuscript (Cooley, H.M., Klaverkamp, J.F., 2000. Accumulation and distribution of dietary uranium in Lake whitefish (Coregonus clupeaformis), Aquat. Toxicol., 48, 375-392), was evaluated. Whole organism morphometrics were unaltered by U exposure. Haematological variables were either unchanged or only transiently affected. Liver and kidney metallothionein concentrations were largely unaltered. Concentrations of serum lipid peroxides were significantly elevated in all treatment groups on days 30 and 100, indicating that U may damage cellular and sub-cellular membranes. Dose- and duration-dependent histopathologies were present in liver and posterior kidney of treated lake whitefish. The most consistent and pronounced lesions in liver were focal hepatocyte necrosis and alterations of bile ductule epithelium. Dose- and duration-dependent renal lesions were most evident in proximal tubules. However, we observed a range of histopathologies in this organ, including tubular necrosis, inflammation, haemorrhaging, depletion of haematopoietic tissues, alterations of distal tubules and collecting ducts, tubule dilation, pigmented macrophage proliferation, and glomerular lesions. Pathologies were observed in lake whitefish at all concentrations of dietary U following prolonged exposure. When used in conjunction with U tissue residue analyses, histopathological lesions and indices of lipid peroxidation may prove useful indicators of U toxicity when assessing fish health in U biomonitoring programmes.