A Method to Quantify and Correct for Edge Leaks in Ussing Chambers

A technique is presented which allows edge leaks in Ussing chambers to be detected and quantified. It is based on the fact that in leaky chambers direct current or low frequency alternating current passes preferentially around the edge of the tissue, while high frequency alternating current shunts the cell membranes and distributes homogeneously through the entire chamber. By measuring the current density in the center of the chamber with low and high frequency alternating current and using correction factors which account for the shape of the electrical field as a function of chamber geometry and of estimated tissue resistance, edge leaks can be quantified. This technique allows correct transepithelial resistance values to be obtained from leaky measurements, and enables the question of whether a given discrepancy between cellular and transepithelial resistances reflects leaky tight junctions or a leaky chamber or both to be answered.