title: Electrical properties of the otic vesicle epithelium in the chick embryo.
abstract: The electrophysiological properties of the epithelium of the otic vesicle were studied in the chick embryo using conventional microelectrode techniques. A preparation is described that allows continuous recording of transmural potential and resistance during changes in the composition of the bathing fluid. Vesicles in stages 18 to 22 showed a spontaneous transmural potential (ET) that ranged from 2 to 6 mV, inner positive. This electrical potential difference was abolished after 2 h incubation in K+-free strophantidin (10(-4) M) and it increased by about twofold immediately after addition of the cation ionophore Amphotericin B (250 microM) to the bath. The specific resistance of the wall (RT) was about 80 omega cm2 between stages 18 and 22 indicating a low-resistance, noncellular, permeation pathway for current flow. The short-circuit current, calculated from ET and RT was about 50 X 10(-6) A cm-2 throughout this period. This corresponds to a net flux of 187 X 10(-8) mol cm-2 h-1 of a single cation pumped towards the towards the vesicular cavity. Diffusion potentials (salt gradients and single-ion substitutions) showed a selectivity ratio PK:PNa:PCl = 1:0.9:0.7, which is that of a weakly charged aqueous pathway. Measurements of vesicular volume and surface area showed an increase by a factor of ten in the size of the vesicle with maximal rates of change in volume of 5 microliter cm-2 h-1. The electrical properties reported here for the epithelium of the otic vesicle resemble very much those of 'leaky' epithelia which are known to transport ions and water at a very high rate.
mesh_terms: D000666:Amphotericin B / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002642:Chick Embryo; D004058:Diffusion; D007758:Ear, Inner / Q000502:physiology*; D004553:Electric Conductivity; D004594:Electrophysiology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D000666:Amphotericin B; D012964:Sodium; D011188:Potassium