Claudins are tight junction membrane proteins that act as paracellular pores and barriers and regulate epithelial permeability to small ions. A key step in understanding the function of any claudin isoform is the in vitro measurement of its ion permeability and selectivity. Herein, we describe methods to generate clonal lines with stable inducible overexpression of claudins in Madin–Darby canine kidney epithelial cells, measure conductance and diffusion potentials in Ussing chambers, correct for liquid junction potentials, and derive quantitatively accurate values for individual ion permeabilities.
