Binding of brominated diphenyl ethers to male rat carrier proteins

1. Two [C-14]-labelled brominated diphenyl ethers, 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) and decabromodiphenyl ether (BDE-209), were separately administered to the male Sprague-Dawley rat as a single oral dose (2.2 mg kg(-1) body weight and 3.0 mg kg(-1) respectively). 2. Very low [C-14] urine excretion was observed for both congeners (< 1% of the dose), and cumulative biliary excretion was approximately 4% for BDE-99 and 9% for BDE-209. 3. More than 6% of the pooled urine from the BDE-99-treated rat was protein-bound to an 18-kDa protein characterized by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western immunoblot analysis as α(2u)-globulin. Eighteen per cent of the radioactivity from the pooled urine from the BDE-209 treated rat was bound to albumin; no binding to α(2u)-globulin was detected. 4. In bile, 27-39% of the radioactivity from the BDE-99-dosed rat was bound to an unidentified 79-kDa protein, whereas essentially all (> 87%) of the biliary radioactivity from BDE-209 was bound to the 79-kDa protein. Both parent BDE-99 and -209 and their metabolites were detected by thin layer chromatography in the extracted fraction of this bile protein. 5. By differential centrifugation, the subcellular localization of the C-14 derived from each congener in selected tissues was quantified. The cytosolic [C-14] from livers of the BDE-209-treated rat was bound to a 14-kDa protein, which was characterized as a fatty acid-binding protein.