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EVALUATION OF PERFLUOROOCTANE SULFONATE (PFOS) IN THE RAT BRAIN
Citation:
LAU, C. S., J. R. THIBODEAUX, D. EHRESMAN, S. TANAKA, J. FROEHLICH, AND J. BUTENHOFF. EVALUATION OF PERFLUOROOCTANE SULFONATE (PFOS) IN THE RAT BRAIN. Presented at International Symposium on Fluorinated Alkyl Organics in the Environment, Toronto, ON, CANADA, August 19 - 20, 2005.
Description:
This study examined whether there is a differential distribution of PFOS within the brain, and compares adult rats with neonatal rats at an age when formation of the blood-brain barrier is not yet complete (postnatal day 7). Male and female Sprague-Dawley rats (60-70 day old, 4/sex) were treated with 3 mg PFOS per kg per day by gavage for 14 days and sacrificed 24 h after the last administration. A blood sample was obtained from tail-bleed prior to sacrifice, and the brain was perfused with isotonic saline. Five brain regions, which included cerebral cortex (CX), hippocampus (HP), cerebellum (CB), hypothalamus (HT), and brainstem (BS), were dissected immediately and stored frozen at -80o C until analysis. For the developmental study, four timed-pregnant dams were given PFOS (3 mg/kg) from gestational day (GD) 2 through GD 21 and allowed to deliver litters. Male and female pups from each litter were sacrificed on postnatal day 7, and their brains were perfused and dissected similarly to the adults. Trunk blood was obtained from littermates after decapitation. Extraction of brain tissues homogenates employed a base digestion followed by a solid phase extraction at an acidic pH for optimal recovery. A 15-�L injection was introduced to the mass spectrometer through a high performance liquid chromatography system. All quantitative calculations for PFOS were based on the ion ratios between PFOS and the stable-isotope-labeled internal standard (dual substituted 18O-PFOS). Mean serum concentrations were 123 mg/mL and 52 mg/mL for adults and pups, respectively. Mean corresponding concentrations (mg/g) in brain regions ranged from approximately 5 to 8 in adults and approximately 15 to 29 in neonates. Brain region mean PFOS concentrations expressed as percentage of mean serum PFOS concentrations ranged from approximately 4 to 6 in adults and 29 to 55 in neonates. Male and female values were similar. From these data, it is evident that PFOS can be detected in the adult rat brain after subchronic exposure, although the extent is limited (ca. 4-6% of the serum level) and there is no differential distribution or accumulation within the brain. In comparison, higher PFOS concentrations were found in the postnatal day 7 neonatal rat brain, most likely due to the fact that the blood-brain barrier is not fully functional in rat pups on postnatal day 7. This abstract does not necessarily reflect EPA policy.