Hyposmolality-induced enhancement of ADH action on amiloride-sensitive Isc in renal epithelial A6 cells

Jpn J Physiol. 1997 Feb;47(1):131-7. doi: 10.2170/jjphysiol.47.131.


To assess the action of antidiuretic hormone (ADH) and the osmolality of bathing solution on amiloride-sensitive Na+ transport, we measured the amiloride-sensitive short-circuit current (Isc) and single-channel currents in renal epithelial A6 cells. The A6 cells were cultured on permeable supports for 9-13 d without aldosterone treatment. The basal amiloride-sensitive Isc and the density of the amiloride-sensitive Na+ channel at the apical membrane increased as the osmolality of the bathing solution decreased. ADH stimulated the amiloride-sensitive Isc. The stimulatory action of ADH was enhanced by low osmolality. The stimulatory action of hyposmolality on the amiloride-sensitive Isc was significantly diminished by pretreatment with brefeldin A (BFA, a blocker of protein translocation), while BFA had no significant effect on the ratio of ADH-stimulated amiloride-sensitive Isc to basal amiloride-sensitive Isc. These results suggest that hyposmolality stimulates the translocation of amiloride-sensitive Na+ channels to the apical membrane from the cytosolic store sites of the channel, and that ADH may activate amiloride-sensitive Na+ channels pre-existing in the apical membrane or translocate the channel via BFA-insensitive pathways in a manner dependent on the osmolality of the bathing solution in aldosterone-untreated A6 cells, differently from aldosterone-treated A6 cells in which ADH stimulates the translocation of amiloride-sensitive Na+ channels via BFA-sensitive pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / pharmacology*
  • Brefeldin A
  • Cell Line
  • Cyclopentanes / pharmacology
  • Diuretics / pharmacology*
  • Electric Conductivity
  • Epithelial Cells
  • Epithelium / drug effects
  • Epithelium / physiology
  • Hypotonic Solutions / pharmacology
  • Kidney / cytology
  • Kidney / drug effects*
  • Kidney / physiology*
  • Osmolar Concentration
  • Protein Synthesis Inhibitors / pharmacology
  • Renal Agents / pharmacology*
  • Vasopressins / pharmacology*


  • Cyclopentanes
  • Diuretics
  • Hypotonic Solutions
  • Protein Synthesis Inhibitors
  • Renal Agents
  • Vasopressins
  • Brefeldin A
  • Amiloride