The Journal of Membrane Biology

, Volume 87, Issue 1, pp 67–75

Effects of internal and external pH on amiloride-blockable Na+ transport across toad urinary bladder vesicles

  • Haim Garty
  • Ethan D. Civan
  • Mortimer M. Civan
Articles

DOI: 10.1007/BF01870700

Cite this article as:
Garty, H., Civan, E.D. & Civan, M.M. J. Membrain Biol. (1985) 87: 67. doi:10.1007/BF01870700

Summary

We have examined the effect of internal and external pH on Na+ transport across toad bladder membrane vesicles. Vesicles prepared and assayed with a recently modified procedure (Garty & Asher, 1985) exhibit large, rheogenic, amiloridesensitive fluxes. Of the total22Na uptake measured 0.5–2.0 min after introducing tracer, 80±4% (mean±se,n=9) is blocked by the diuretic with aK1 of 2×10−8m. Thus, this amiloridesensitive flux is mediated by the apical sodium-selective channels. Varying the internal (cytosolic) pH over the physiologic range 7.0–8.0 had no effect on sodium transport; this result suggests that variation of intracellular pHin vivo has no direct apical effect on modulating sodium uptake. On the other hand,22Na was directly and monotonically dependent on external pH. External acidification also reduced the amiloride-sensitive efflux across the walls of the vesicles. This inhibition of22Na efflux was noted at external Na+ concentrations of both 0.2 μm and 53mm.

These results are different from those reported with whole toad bladder. A number of possible bases for these differences are considered and discussed. We suggest that the natriferic response induced by mucosal acidification of whole toad urinary bladder appears to operate indirectly through one or more factors, presumably cytosolic, present in whole cells and absent from the vesicles.

Key Words

sodium channels pH dependence mucosal acidification intracellular pH apical Na+ entry Na+ permeability 

Copyright information

© Springer-Verlag 1985

Authors and Affiliations

  • Haim Garty
    • 1
  • Ethan D. Civan
    • 1
  • Mortimer M. Civan
    • 1
  1. 1.Department of Membrane ResearchThe Weizmann Institute of ScienceRehovotIsrael
  2. 2.College of Arts and SciencesUniversity of PennsylvaniaPhiladelphia
  3. 3.Departments of Physiology and MedicineUniversity of Pennsylvania School of MedicinePhiladelphia

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