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: 286/6/C1399    most recent 00198.2003v1 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 ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (9) Citing Articles via Google Scholar Google Scholar Articles by Ordaz, B. Articles by Pasantes-Morales, H. Search for Related Content PubMed PubMed Citation Articles by Ordaz, B. Articles by Pasantes-Morales, H.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Volume changes and whole cell membrane currents activated during gradual osmolarity decrease in C6 glioma cells: contribution of two types of K⁺ channels

¹Department of Biophysics, ²Department of Cell Biology, Institute of Cell Physiology, National University of Mexico, Mexico City, Mexico

Submitted 14 May 2003 ; accepted in final form 15 January 2004

Volume changes and whole cell ionic currents activated by gradual osmolarity reductions (GOR) of 1.8 mosM/min were characterized in C6 glioma cells. Cells swell less in GOR than after sudden osmolarity reductions (SOR), the extent of swelling being partly Ca²⁺ dependent. In nominally Ca²⁺-free conditions, GOR activated predominantly whole cell outward currents. Cells depolarized from the initial –79 mV to a steady state of –54 mV reached at 18% osmolarity reduction [hyposmolarity of –18% (H-18%)]. Recordings of Cl^– and K⁺ currents showed activation at H-3% of an outwardly rectifying Cl^– current, with conductance of 1.6 nS, sensitive to niflumic acid and 5-nitro-2-(3-phenylpropylamino)benzoic acid, followed at H-18% by an outwardly rectifying K⁺ current with conductance of 4.1 nS, inhibited by clofilium but insensitive to the typical K⁺ channel blockers. With 200 nM Ca²⁺ in the patch pipette, whole cell currents activated at H-3% and at H-13% cells depolarized from –77 to –63 mV. A K⁺ current activated at H-1%, showing a rapid increase in conductance, suppressed by charybdotoxin and insensitive to clofilium. These results show the operation of two different K⁺ channels in response to GOR in the same cell type, activated by Ca²⁺ and osmolarity and with different osmolarity activation thresholds. Taurine and glutamate efflux, monitored by labeled tracers, showed delayed osmolarity thresholds of H-39 and H-33%, respectively. This observation clearly separates the Cl^– and amino acid osmosensitive pathways. The delayed amino acid efflux may contribute to counteract swelling at more stringent osmolarity reductions.

volume regulation; taurine; hyposmolarity; isovolumetric regulation; regulatory volume decrease

This article has been cited by other articles:

				S. B. Ross, C. M. Fuller, J. K. Bubien, and D. J. Benos Amiloride-sensitive Na+ channels contribute to regulatory volume increases in human glioma cells Am J Physiol Cell Physiol, September 1, 2007; 293(3): C1181 - C1185. [Abstract] [Full Text] [PDF]