Summary
When tracer Na+ is added to the solution bathing the apical side of isolated epithelia the observed transepithelial tracer influx increases with time until a steady state is reached. The build-up of the tracer flux follows a single exponential course. The halftime for this build-up under control conditions was 0.92 ±0.06 min, and in the presence of ouabain 4.51±0.7 min. It is shown that the calculated Na+-transport pool is located in the cells. The Na+-transport pool under control conditions was 35.6 ±3.4 nmol/cm2, which corresponds to an intracellular Na+ concentration of 7.9mm. Activation of the active Na+ transport by addition of antidiuretic hormone resulted in a highly significant increase in the Na+ transport pool, and inhibition of the transcellular Na+ transport with amiloride resulted in a decrease in the Na+-transport pool.
Furthermore, the active Na+ transport increased along anS-shaped curve with increasing intracellular Na+ concentration (Na+-transport pool). The Na+ pump was found to be half saturated at an intracellular Na+ concentration of 12.5mm.
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Nielsen, R. Effect of ouabain, amiloride, and antidiuretic hormone on the sodium-transport pool in isolated epithelia from frog skin (Rana temporaria). J. Membrain Biol. 65, 221–226 (1982). https://doi.org/10.1007/BF01869965
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DOI: https://doi.org/10.1007/BF01869965