BIOTRANSFORMATION OF THE 82 FLUOROTELOMER ACRYLATE IN RAINBOW TROUT 2 IN VITRO INCUBATIONS WITH LIVER AND STOMACH S9 FRACTIONS

The biotransformation of the 8 2 fluorotelomer acrylate (C8F17CH2CH2OC(O)CH = CH2 8 2 fluorotelomer based acrylate [FTAc] was quantitatively investigated in cytosolic (S9) fractions isolated from rainbow trout stomach and liver The in vitro studies presented in this manuscript compliment the whole body 8 2 FTAc dietary exposure study presented as a companion paper The S9 fractions were prepared in our laboratory using fish that had previously been used as control animals in our in vivo study Before 8 2 FTAc incubations general carboxylesterase activity was determined using paranitrophenyl acetate (PNPA) as the substrate with formation of paranaitrophenol monitored using an ultraviolet vis spectrometer In the 8 2 FTAc incubations the degradation of the parent compound and 8 2 fluorotelomer alcohol (FTOH) formation was monitored by gas chromatography mass spectrometry Incubations were performed in triplicate over a range of concentrations encompassing two orders of magnitude and the initial rate of 8 2 FTOH or paranitrophenol formation was determined Enzyme kinetic parameters were determined by plotting the initial rate versus concentration using nonlinear regression analysis The maximum initial velocities of the enzyme catalyzed reaction (V-max) in the PNPA incubations were 614 +/- 18 nmol/min/mg and 147 +/- 16 nmol/min/mg for the liver and stomach fractions respectively These values are much faster than other phase I and II metabolism reactions The calculated intrinsic clearance rates (CLim) for the 8 2 FTAc incubations were 1 7 and 040 ml/min/mg protein respectively These results show that the esterase activity toward the 8 2 FTAc is only fourfold greater in the liver as compared with the stomach These trends demonstrate the potential for considerable extrahepatic metabolism of the 8 2 FTAc before uptake into the internal tissues ultimately limiting the overall bioaccumulation Environ Toxicol Chem 2010 29 2736-2741 (C) 2010 SETAC