HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 294/5/C1133    most recent 00315.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Webb, K. F. Articles by Donaldson, P. J. Search for Related Content PubMed PubMed Citation Articles by Webb, K. F. Articles by Donaldson, P. J.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Differentiation-dependent changes in the membrane properties of fiber cells isolated from the rat lens

Department of Physiology, School of Medical Sciences, University of Auckland, Auckland, New Zealand

Submitted 22 July 2007 ; accepted in final form 20 March 2008

Impedance measurements in whole lenses showed that lens fiber cells possess different permeability properties to the epithelial cells from which they differentiate. To confirm these observations at the cellular level, we analyzed the membrane properties of fiber cells isolated in the presence of the nonselective cation channel inhibitor Gd³⁺. Isolated fiber cells were viable in physiological [Ca²⁺] and exhibited a range of lengths that reflected their stage of differentiation. Analysis of a large population of fiber cells revealed a subgroup of cells whose conductivity matched values measured in the whole lens (1). In this group of cells, membrane resistance, conductivity, and reversal potential all varied with cell length, suggesting that the process of differentiation is associated with a change in the membrane properties of fiber cells. Using pharmacology and ion substitution experiments, we showed that newly differentiated fiber cells (<150 µm) contained variable combinations of Ba²⁺-and tetraethylammonium-sensitive K⁺ currents. Longer fiber cells (150–650 µm) were dominated by a lyotropic anion conductance, which also appears to plays a role in the intact lens. Longer cells also exhibited a low-level, nonselective conductance that was eliminated by the replacement of extracellular Na⁺ with N-methyl-D-glucamine, indicating that the lens contains both Gd³⁺-sensitive and -insensitive nonselective cation conductances. Fiber cell differentiation is therefore associated with a shift in membrane permeability from a dominant K⁺ conductance(s) toward larger contributions from anion and nonselective cation conductances as fiber cells elongate.

electrophysiology; potassium channel; anion channel; nonselective cation channel