TEER Measurement

Transepithelial electrical resistance (TEER) measurements were made using an EVOM meter (World Precision Instruments) and chopstick-style electrodes as done previously [41] and by others [42]. Briefly, mCCDcl1 cells were seeded on to Corning Costar^™ Transwell^™ Permeable Supports (0.4 μm pore size) in 24 well plates at 1×10⁵ cells/cm² in complete growth medium. After 7–9 days, cell monolayer formation in transwell cups was assessed by measuring TEER where all monolayers reached TEER values of 1000 Ω cm² or more, which was taken as an index of achieving monolayer confluency. Whereupon, the cells were incubated in base medium for another 2 days before performing the experiments. All TEER measurements were made at 37°C in base media. Under these conditions the monolayers displayed an average TEER reading of 3081 ± 155 Ω cm² (n = 15) during basal conditions.