Modulation of uranium bioaccumulation by hypoxia in the freshwater clam Corbicula fluminea: induction of multixenobiotic resistance protein and heat shock protein 60 in gill tissues.

The influence of hypoxia on the bioaccumulation of uranium in the clam Corbicula fuminea was investigated in ecologically relevant conditions. The cellular impact at the gill-tissue level was assessed by analyzing the induction of multixenobiotic resistance protein (MXR) and heat shock protein 60. Analyses were performed at three biological levels. First, at the organism level, uranium induced a significant decrease in the valve open duration under normoxia, but not under hypoxia, in which oxygen drive imposed an increase of the valve open duration. Second, at the tissue level, the uranium bioaccumulation rate in the gills was higher under hypoxia than under normoxia. Third, at the cellular level, MXR was induced by uranium but not by hypoxia. The threshold of tissular uranium concentration triggering MXR induction was between 3 and 5 nmol/g. On the contrary, Hsp60 was induced by hypoxia but not by uranium.