Side-view illustration of an RPE cell showing the three main pathways where ion transport is regulated.

Illustration showing a cross-section of epithelial tissue and additional pathways of ion transport that are measurable with 3 P-EIS. With electrodes placed at nodes 1, 2, and 3, 3 P-EIS can predict the apical resistance and capacitance (Ra and Ca), the basolateral resistance and capacitance (Rb and Cb), and the shunt (Rs) properties of epithelial tissues.

A) Cross-sectional illustration of a modified Ussing chamber, used to measure the electrical properties of epithelial tissues. B) Photo of a modified Ussing chamber. C) Glass pipette used to measure charge inside individual epithelial cells. The pipette’s tip is too small to be seen with the naked eye. D) NEI researchers Colby Lewallen, Ph.D. (left) Arvydas Maminishkis, M.D., Ph.D., and Qin Wan, Ph.D. readying an Ussing chamber.