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(087) Biotransformation of perfluorooctane sulfonamide by trout liver microsomes in vitro.
Tomy, Gregg1, Palace, Vince*,1, Braekevelt, Eric1, Tittlemier, Sheryl2, Lau, Ben2, Eales, Geoff3, Plohman, James3, 1 Department of Fisheries and Oceans, Winnipeg, Manitoba, Canada2 Health Canada, Food Research Division, Ottawa, Ontario, Canada3 University of Manitoba, Winnipeg, Manitoba
ABSTRACT- Rainbow trout liver microsomes were exposed to perfluorooctane sulfonamide (PFOSA, C8F17SO2NH2), a surfactant used in the surface treatment of textiles and paper to increase stain-resistance. The experiment was performed to examine the possibility of in vitro PFOSA biotransformation. Each assay contained 1 mg of microsomal protein in 0.05 M phosphate buffer (pH=7.0) with 1ng/ml of PFOSA. After incubations of 0, 2, 8, 16, 24 and 30 hours at 10oC, reactions were terminated by the addition of an equal volume of HPLC grade methanol. The ion-pairing reagent tetrabutylammonium hydrogen sulfate (TBA, pH =10) was added to the solution and extracted with methyl tert-butyl ether buffered with sodium carbonate. Perfluorooctane sulfonate (PFOS, C8F17SO3-) was detected in all of the microsome aliquots sampled. The concentration of PFOS increased in the aliquots over time, suggesting a conversion of PFOSA to PFOS. This conversion appeared to be a first-order kinetic reaction. The rate constant of formation (kH) of PFOS was determined to be 0.094 hr-1. This represents the first report indicating a possible biotransformation of PFOSA to PFOS in fish.
Key words: perfluorooctanesulfonate, in vitro, metabolism, biotransformation
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