LOCALIZING TRANSEPITHELIAL CONDUCTIVE PATHWAYS USING A VIBRATING VOLTAGE PROBE

A model simulation of the electrical field distribution for the voltag e-activated Cl- current across amphibian skin has been carried out for two potential pathways, i.e. transcellularly, through the mitochondri a-rich cells (MRCs), or paracellularly, across the tight junctions (TJ s) between the outermost living cell layer, The calculations are based on the mean density of MRCs and the typical dimensions of stratum gra nulosum cells of amphibian skin. It is demonstrated that current flow across MRCs would be detectable by scanning with the vibrating voltage probe in the extracellular space above the epithelium, whereas accura te representation of current how through the TJs cannot be obtained us ing a probe of the present design. The experimental data indicate that field patterns corresponding to an MRC origin for the Cl- current are never observed. It is concluded that the voltage-activated Cl- conduc tance is localized to ion-selective structures in the paracellular pat hway which may be regulated by the TJs.