Letter | Published:

Active sodium transport by turtle colon via an electrogenic Na–K exchange pump

Naturevolume 287pages237239 (1980) | Download Citation

Subjects

Abstract

Active sodium absorption by a variety of epithelia is abolished by ouabain, but the obligatory coupling between the movement of sodium and potassium expected from a basolateral (Na+ + K+) ATPase has not been convincingly demonstrated1. According to the model of Koefoed-Johnsen and Ussing2, the asymmetric cation selectivities of the apical and basolateral membranes prevent basolateral Na–K exchange from being expressed as opposing transmural ion flows. An additional consequence of this asymmetry is that the short-circuit current (ISC) cannot be identified with the current through the sodium–potassium pump. We used the polyene antibiotic, amphotericin-B, to reduce the resistance and the cation selectivity of the apical membrane of isolated turtle colon so that the basolateral membrane current could be dissected into two components: one through a barium-sensitive potassium channel and another which represents the current associated with ouabain-sensitive, electrogenic, Na–K exchange. Comparison of cation fluxes and short circuit current indicates that in these conditions active sodium absorption is entirely attributable to an electrogenic Na–K pump with a stoichiometry of approximately 3Na:2K.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Schultz, S. G. Membrane Transport Processes Vol. 1 (ed. Hoffman, J. F.) 213–117 (1978).

  2. 2

    Koefoed-Johnson, V. & Ussing, H. H. Acta physiol. scand. 42, 298–308 (1958).

  3. 3

    Dawson, D. C. J. Membrane Biol. 37, 213–233 (1977).

  4. 4

    Thompson, S. M. & Dawson, D. C. J. Membrane Biol. 42, 357–374 (1978).

  5. 5

    Marty, A. & Finkelstein, A. J. gen Physiol. 65, 515–526 (1975).

  6. 6

    Cass, A. & Dalmark, M. Nature new Biol. 244, 47–49 (1973).

  7. 7

    Nielsen, R. J. Membrane Biol. 51, 161–184 (1979).

  8. 8

    Lewis, S. A., Eaton, D. C., Clausen, C. & Diamond, J. M. J. gen Physiol. 70, 427–440 (1977).

  9. 9

    Reuss, L. J. Membrane Biol. 42, 65–86 (1978).

  10. 10

    Nagel, W. Biochim. biophys. Acta 552, 346–357 (1979).

  11. 11

    Post, R. L. & Jolly, P. C. Biochim. biophys. Acta 25, 108–128 (1957).

  12. 12

    Hoffman, J. F., Kaplan, J. H. & Callahan, T. J. Fedn Proc. 38, 2440–2441 (1979).

  13. 13

    Thomas, R. C. Physiol. Rev. 52, 563–594 (1972).

Download references

Author information

Affiliations

  1. Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa, 52240

    • Kevin L. Kirk
    • , Dan R. Halm
    •  & David C. Dawson

Authors

  1. Search for Kevin L. Kirk in:

  2. Search for Dan R. Halm in:

  3. Search for David C. Dawson in:

About this article

Publication history

Received

Accepted

Issue Date

DOI

https://doi.org/10.1038/287237a0

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.