Assessing Barrier Integrity and Permeability

Barrier integrity or monolayer tightness was assessed by measuring transendothelial electrical resistance (TEER) while using a Millicell ERS electrode (Millipore, Bedford, MA, USA). Paracellular permeability was assessed in monolayers by measuring the diffusion profile of 0.1 µCi of [¹⁴C] sucrose (PerkinElmer, Waltham, MA, USA). Radioactivities of samples were counted using a liquid scintillation counter (PerkinElmer, Waltham, MA, USA). The permeability coefficient was calculated while using following formula [34 (link)]: $PC=\frac{dQ}{dt}\times \frac{1}{A\times C_0}$
where dQ/dt is rate of [¹⁴C] sucrose diffusion, A is area of insert, and C₀ is the initial concentration of [¹⁴C] Sucrose added in donor compartment.