Sodium and potassium flux of separated renal tubules

¹ Laboratory of Kidney and Electrolyte Metabolism, National Heart Institute, National Institutes of Health, Bethesda, Maryland

The Na and K fluxes of renal tubule cells were measured using suspensions of tubules separated from rabbit renal cortex. Kinetic analysis indicates that there are at least two Na compartments and two K compartments in the tubules. The rates at which Na and K exchanged were considerably greater than in renal cortical slices in accordance with predictions based on considerations of the geometrical arrangement of the cells in slices. Digitalis-like steroids, known to depress active cation transport, lowered the efflux rate constant for Na from the major Na compartment and diminished both K influx and the K efflux rate constants. The calculated active efflux of Na greatly exceeded the influx of K, indicating that active Na and K transport are not coupled in a 1:1 ratio.

Key Words: rabbit kidney tubules • active cation transport • cardiotonic steroids and tubular transport • transmembrane ion exchange • cellular Na and K compartments

Submitted on June 17, 1963