Ls 180 cells

PIs amprenavir, saquinavir and lopinavir were generous gifts from (GlaxoSmithKline, Brentford, Middlesex, UK), (Roche, Basel, Switzerland) and (Abbott Laboratories, Chicago, IL, USA), respectively. Indinavir was purchased from Fisher Scientific (Fair Lawn, NJ, USA). LS-180 cells were obtained from American Type Culture Collection (Manassas, VA, USA). [¹⁴C]Erythromycin (specific activity: 51.3 mCi/ mmol) was procured from Moravek Biochemicals (Brea, CA, USA). TrypLE™ Express, Dulbecco's modified Eagle's medium (DMEM), Vivid^® CYP450 Screening Kit and ATP determination kit were obtained from Invitrogen (Carlsbad, CA, USA). OligodT, dNTP, MgCl₂, M-MLV Reverse Transcriptase and CellTiter 96^® Non-Radioactive Cell Proliferation Assay (MTT) were purchased from Promega Corporation (Madison, WI, USA). LightCycler 480^® SYBR I Green Master Mix was obtained from Roche Applied Science (Indianapolis, IN, USA). Fetal bovine serum (FBS) was purchased from Atlanta Biologicals (Lawrenceville, GA, USA). Culture flasks (75 cm² growth area), 12-well plates (3.8 cm² growth area per well) and 96-well plates (0.32 cm² growth area per well) were purchased from Corning Costar Corp. (Cambridge, MA, USA). All other chemicals were products of commercial grade and were purchased from Sigma Chemicals (St. Louis, MO, USA) and Fisher Scientific.