Repolarization of Na+-K+ pumps during establishment of epithelial monolayers. Academic Article uri icon

Overview

abstract

  • Madin-Darby canine kidney (MDCK) cells plated at confluence and incubated for 20 h in low (5 microM) Ca2+ have no tight junctions (TJs), and their Na+-K+-ATPase is randomly distributed over the surface. On transfer to normal Ca2+ levels (1.8 mM) ("Ca2+ switch"), TJs and transepithelial resistance develop quickly, trapping a considerable fraction (35%) of the surface Na+-K+-ATPase on the apical (incorrect) side. This misplaced enzyme is subsequently removed from this region or inactivated, demonstrating that polarization proceeds despite TJs. Simultaneously, the amount of Na+-K+-ATPase on the basolateral side increases in a higher proportion (125%), than could be accounted for by relocation of the misplaced apical enzyme. This incorporation is prevented by cycloheximide, ammonium chloride, primaquine, or chloroquine, suggesting that Na+-K+-ATPase originates in an intracellular pool and that its surface insertion requires synthesis of new enzyme or of a protein factor, since it is carried to the surface membrane through a mechanism of exocytosis. In summary, asymmetric distribution of ion pumps depends 1) on polarized insertion of Na+-K+-ATPase as well as 2) on removal or inactivation of misplaced enzyme.

publication date

  • November 1, 1989

Research

keywords

  • Epithelium
  • Ion Channels
  • Sodium-Potassium-Exchanging ATPase

Identity

Scopus Document Identifier

  • 0024306467

Digital Object Identifier (DOI)

  • 10.1152/ajpcell.1989.257.5.C896

PubMed ID

  • 2480715

Additional Document Info

volume

  • 257

issue

  • 5 Pt 1