CYP2B6 and steatosis: The purpose of this study is to (1) test whether there are specific oxylipins associated with PFOS toxicity that may help explain or provide markers of differential toxicity and steatosis between normal diet-fed Cyp2b-null and hCYP2B6-Tg mice, (2) to estimate the mechanism of PFOS toxicity on the liver as tested by transcriptomics, and (3) to determine parameters that are associated with and likely to increase retention in hCYP2B6-Tg mice in comparison to Cyp2b-null mice.