Rapid determination of intraepithelial resistance barriers by alternating current spectroscopy. I. Experimental procedures.

A method has been developed to determine rapidly and simultaneously the resistance of the tight junctions, the resistance of the lateral intercellular space, and the resistances and capacitances of the apical and basolateral cell membrane in leaky epithelia by alternating current spectroscopy. The present paper describes the experimental procedures. Multi-frequency sine-wave currents are simultaneously applied across the tissue and the transepithelial and intracellular voltage responses are recorded with shielded microelectrodes, digitized, and stored in a computer. Using Fast Fourier Transform techniques the frequency-dependent transepithelial impedance and an apparent basal cell membrane impedance are then calculated from the voltage and current waveform. By fitting appropriate model circuits to the data the above listed individual resistances can be deduced. The model calculations and the fit results are described in the subsequent paper [14]. In the present design the analysis covers the frequency range between 2.5 Hz and 12.5 kHz. The minimal measuring time is in the order of 1-2s.