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Intracellular C1, K and Na activities (a Cl i ,a k i anda Na i ) and transmucosal membrane potential (E m) in epithelial cells ofNecturus gallbladder were measured at different external Na concentrations ([Na]o), with liquid ion-exchanger and conventional microelectrodes. Bladders were mounted in a divided chamber at 23°C between identical HCO3-free Ringer(More)
Intracellular Na+, K+, and Cl− activities (a Na i ,a K i ,a Cl i ) and transapical membrane potentials (V o) were measured with liquid ion-exchanger and open-tip microelectrodes in isolated short-circuited frog skins (R. pipiens) incubated at 23°C in normal amphibian Ringer's solution. Under control conditionsa Na i =14±3mm,a K i =132±10mm anda Cl i =18±3mm(More)
Open-tip and Cl−-selective microelectrodes were used to study the effect of external pH on apical membrane potential (V a) and intracellular chloride activity (a Cl i ) in epithelial cells ofNecturus gallbladder. Increasing the pH from 7.2 to 8.2 in the mucosal, the serosal, or in both bathing solutions simultaneously, hyperpolarizedV a (control value −60±5(More)
Na+, K+ and Cl- concentrations (cij) and activities (aij), and mucosal membrane potentials (Em) were measured in epithelial cells of isolated bullfrog (Rana catesbeiana) small intestine. Segments of intestine were stripped of their external muscle layers, and bathed (at 25 degrees C and pH 7.2) in oxygenated Ringer solutions containing 105 mM Na+ and Cl-(More)
This report reviews the use of ion-selective microelectrodes to measure intracellular ionic activities and ionic electrochemical potential differences across cell membranes. Particular emphasis is placed on the electrochemical characteristics of liquid ion-exchanger microelectrodes. Methods for assessing the effect of interfering ions on the electrode(More)
It has been suggested that distribution of lateral interspace resistance in association with a highly conductive junction can significantly affect the measurement of outer membrane(o)/epithelial(t) voltage divider ratios (F o=δV o/δV t), thereby leading to erroneous inferences regarding the outer membrane fractional resistance [fR o=R o/R c=R o/(R o+R i)],(More)
The sodium-selective ligand 1,1,1-tris[1(1)-(2(1)-oxa-4(1)-oxo-5(1)-aza-5(1)-methyl)dodecanyl]propane dissolved in 3-nitro-o-xylene containing a small amount of the lipophilic anion tetrachlorophenyl borate was used as a liquid ion-exchanger in sodium-selective microelectrodes. The microelectrodes gave rapid, stable responses that were linear functions of(More)
Cell K activity,a k, 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)
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)