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The effects of serosal substitution of isosmotic Na2SO4-Ringer solution for NaCl-Ringer solution were studied in the short-circuited frog skin (Rana pipiens, Northern variety). Despite prompt changes of transepithelial measurements, initial cellular effects were slight. After 30 to 45 min, however, the transcellular current had decreased and the cell(More)
In the isolated bullfrog cornea epithelium, under short-circuit conditions the regulation of the K permeability of the basolateral membrane was studied with conventional and K-selective microelectrodes in Cl-free Ringers. In Cl-free Ringers, the transcellular current is less than 1 microA/cm2, allowing estimation of the basolateral membrane electromotive(More)
Cell K activity, acK, was measured in the short-circuited frog skin by simultaneous cell punctures from the apical surface with open-tip and K-selective microelectrodes. Strict criteria for acceptance of impalements included constancy of the open-tip microelectrode resistance, agreement within 3% of the fractional apical voltage measured with open-tip and(More)
Cell Na activity, acNa, was measured in the short-circuited frog skin by simultaneous cell punctures from the apical surface with open-tip and Na-selective microelectrodes. Skins were bathed on the serosal surface with NaCl Ringer and, to reduce paracellular conductance, with NaNO3, Ringer on the apical surface. Under control conditions acNa averaged 8 +/-(More)
In studies of apical membrane current-voltage relationships, in order to avoid laborious intracellular microelectrode techniques, tight epithelia are commonly exposed to high serosal K concentrations. This approach depends on the assumptions that high serosal K reduces the basolateral membrane resistance and potential to insignificantly low levels, so that(More)
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