This project characterizes the capacity of hepatic microsomes derived from southeastern Alaska forage fish to remove bromine from polybrominated diphenyl ethers (PBDEs), identify the debromination product distributions and the potential of the debromination process to interfere with the normal function of the relevant hepatic enzymes. The distributions of PBDEs with varying degrees of bromination (i.e. congeners) found in fish species suggests reductive biotransformation is occurring and the structural similarity of PBDEs to thyroid hormones suggests a role in this transformation for the deiodinase enzyme responsible for thyroid homeostasis. Evidence for the role of the deiodinase enzyme in the debromination of PBDEs in situ will be pursued through GCMS analysis of assay extracts. Preliminary results show evidence for the debromination of BDE99 to BDE47 by staghorn sculpin microsomes. Linking biotransformation of BDE99 to the higher proportion of the lesser brominated congeners found in staghorn sculpin follows from the results of this project. Preliminary surveys of tissue from starry flounder show PBDE congeners but distributions differ from those of staghorn sculpin. Work focusing on comparisons of kinetic data and product distributions from both species is planned.
