2.5. Permeability assay
The permeability coefficient of each barrier was measured using
FITC-dextran 3-5 kDa (Sigma, USA, FD4). The amount of FITC-dextran
transported across the cell barrier was measured for 3 h with 1 h term.
The permeability coefficient of each cell barrier was determined using
equation (2).
\begin{equation}
P_{\text{app}}=\frac{C}{t}\times\frac{V}{A*C_{0}}\ \ \ \ \ \ \ \ \ \ \ (2)\nonumber \\
\end{equation}Papp is permeability coefficient (cm/s), C is
basolateral concentration (mg/ml), V is basolateral volume (ml), t is
time (sec), A is cell culture area (cm2), and
C0 is initial apical concentration (mg/ml).