Liver, brain, and plasma samples from C57BL/6J male mice treated for 1 or 8 days with fenofibrate (150 mg/kg; n=6 per group) were collected 2 hours after the final injection and sent to inVentiv Health Clinical Lab, Inc. (Princeton, NJ) for mass spectrometry analysis (LC-MS/MS) to measure levels of fenofibrate and its active metabolite, fenofibric acid. The parent compound, fenofibrate, was not observed at the detection limit of the bioanalytical assay. One part of plasma, brain, or liver was homogenized with 4 parts of lysate in a FastPrep (MP Biomedicals, Santa Ana, CA) homogenizer. After protein precipitation, the samples were analyzed via a Waters Acquity UPLC (Waters Corporation, Milford, MA) with a gradient of 0.1% formic acid in water and 0.1% formic acid in acetonitrile on a BEH C8 2.1×50 1.7 mcm column (Waters Corporation). The internal standards were tolbutamide and warfarin. Samples were quantified by positive LC-ESI-MS/MS-Multiple Reaction Monitoring (MRM) using an API4000 (AB SCIEX, Framingham, MA) at unit/unit resolution with the heater set at 500C, spray voltage at 5000 eV, and CAD gas at 4 and data gathered via Analyst Software (AB SCIEX) and a proprietary Excel program.
