Fig. 1. Transepithelial impedance analysis. (A) Electrical equivalent circuit of the epithelium. See Materials and Methods for explanation. (B) Typical impedance data (open circles) of an C7-cld-2 monolayer (transfected with claudin-2 cDNA) in regular Ringer's solution and in low Ca²⁺ Ringer's. The Nyquist plot shows the real and the imaginary parts of the transepithelial impedance as a function of frequency. Dots on a solid line depict the least-squares fit of the data to the electrical model.