Conductive sodium pathway with low affinity to amiloride in LLC-PK1 cells and other epithelia

A. Moran, C. Asher, E. J. Cragoe, H. Garty

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18 Scopus citations

Abstract

Electrical potential driven 22Na+ fluxes were measured in membrane vesicles prepared from a number of cultured and naturally occurring epithelia. In all preparations a rheogenic pathway blocked by 200 μM (but not by 1.5 μM) amiloride was noted. This transporter was characterized in membranes prepared from cultured LLC-PK1 cells. In this preparation more than 50% of the rheogenic 22Na+ uptake was blocked by amiloride (IC50 ~ 30 μM), phenamil (IC50 ~ 66 μM), or ethylisopropyl amiloride (IC50 ~ 5 μM). This amiloride-sensitive flux was not seen if the vesicles were partially depolarized by external Na+ or K+. It could not be driven by a pH gradient, did not require the presence of Ca2+, sugars, or amino acids, and showed little dependence on temperature (25 versus 0°C). The data suggest the existence of an epithelial amiloride-blockable Na+ transporter different from the previously characterized Na+ channel, Na+/H+ and Na+/Ca2+ exchangers, and the Na+-hexose co-transporter. In rat kidney cortex membranes prepared by Mn2+ precipitation, this transporter is primarily located in the brush-border fraction.

Original languageEnglish
Pages (from-to)19586-19591
Number of pages6
JournalJournal of Biological Chemistry
Volume263
Issue number36
StatePublished - 1 Dec 1988

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