Dietary cadmium induces histopathological changes despite a sufficient metallothionein level in the liver and kidneys of the bank vole (Clethrionomysglareolus)

The objective of this study was to correlate hepatic and renal cadmium (Cd) accumulation: Cd-binding capacity of metallothionein (MT) and lipid peroxi dation with the tissue injury in the male bank voles raised under short (8 h light/16 h dark) and long (16 h light/8 h dark) photoperiods that affect differently Cd accumulation and MT induction in these rodents. The animals were exposed to dietary Cd (0, 40 and 80 mu g/g) for 6 weeks. The accumulat ion of Cd in the liver and kidneys appeared to be dose-dependent in bank vo les from the two photoperiod groups. however, the short-photoperiod animals exhibited significantly higher concentrations of Cd in both organs than th e long-photoperiod bank voles. Cd-Binding capacity of MT in the liver and k idneys of bank voles From the long photoperiod was sufficiently high to bin d and detoxify all Cd ions, while in the animals fed 80 mu g Cd/g under the short photoperiod, the concentrations of Cd in both organs exceeded (by ab out 10 mu g/g) the MT capacity. However, similar histopathological changes in the liver (a focal hepatocyte swelling and granuloma) and kidneys (a foc al degeneration of proximal tubules) occurred in Cd-80 bank voles from the two photoperiods. Likewise, in either photoperiod group, dietary Cd brought about a similar, dose-dependent decrease in the hepatic and renal lipid pe roxidation, which paralleled closely that of the iron (Fe) concentrations. These data indicate that: (1) MT does not protect the liver and kidneys aga inst Cd-induced injury in the bank vole exposed to the higher level of diet ary Cd; and (2) lipid peroxidation cannot be responsible for the tissue dam age. It is hypothesized that dietary Cd produces histopathological changes indirectly, through depressing the tissue Fe and Fe-dependent oxidative pro cesses. (C) 2000 Elsevier Science Inc. All rights reserved.