TEER and PD difference measurements

Both primary bronchial and FRT cells were treated with compounds included in the appropriate culture medium at the indicated concentrations for 24 hours at 37°C and 5% CO₂, before measuring the TEER and/or PD. In all experiments, TEER and PD were evaluated with an epithelial voltohmmeter (EVOM1; World Precision Instruments).

For primary bronchial cells, the electrical measurements were done in Coon’s modified Ham’s F12 medium where NaHCO₃ was replaced with 20 mM Na-Hepes (pH 7.3). After equilibration for 1 hour, TEER and PD were measured in each well under basal conditions, after ENaC inhibition with apical amiloride (10 μM), after CFTR stimulation with forskolin (10 μM) and genistein (50 μM) on both sides, and after CFTR inhibition with apical PPQ102 (30 μM). After each treatment, we waited 10 min before recording electrical parameters. The TEER and PD values for each well were converted into short-circuit current equivalent by Ohm’s law.

For FRT cells, experiments were performed in a solution containing 130 mM NaCl, 2.7 mM KCl, 1.5 mM KH₂PO₄, 1 mM CaCl₂, 0.5 mM MgCl₂, 10 mM Na-Hepes (pH 7.3), and 10 mM glucose. We measured TEER under basal conditions with the same solution on both sides of the permeable supports. Then, we added 20 μM forskolin and 50 μM genistein to activate CFTR channels. Last, we added 30 μM PPQ102 to block CFTR. As done for bronchial epithelial cells, we waited 10 min after each treatment before taking the measurement. The TEER values were converted into TEEC.