Summary
Cell Na activity,a cNa , was measured in the short-circuited frog skin by simulaneous 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 conditionsa cNa averaged 8±2mm (n=9,sd). Apical addition of amiloride (20 μm) or Na replacement reduceda cNa to 3mm in 6–15 min. Sequential decreases in apical [Na] induced parallel reductions ina cNa and cell current,I c . On restoring Na after several minutes of exposure to apical Na-free solutionI c rose rapidly\((\tilde< 30\sec )\) to a stable value whilea cNa increased exponentially, with a time constant of 1.8±0.7 min (n=8). Analysis of the time course ofa cNa indicates that the pump Na flux is linearly related toa cNa in the range 2–12mm. These results indicate thata cNa plays an important role in relating apical Na entry to basolateral active Na flux.
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García-Díaz, J.F., Klemperer, G., Baxendale, L.M. et al. Cell sodium activity and sodium pump function in frog skin. J. Membrain Biol. 92, 37–46 (1986). https://doi.org/10.1007/BF01869014
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DOI: https://doi.org/10.1007/BF01869014