Volume regulation in rat brain glial cells: lack of a substantial
contribution of free amino acids.
Mountian, Irina, Peter E. Declercq, and Willy Van Driessche.
Laboratory of Physiology, K. U. Leuven, Gasthuisberg, B-3000,
Leuven, Belgium and Laboratory of Clinical Chemistry, K. U. Leuven,
E. Van Evenstraat, 4, B-3000, Leuven, Belgium
APStracts 2:0416C, 1995.
Volume regulation of C6 glioma cells was studied while reducing the
bath osmolality from 300 to 150 mmol/l. Exposure to a hyposmotic
challenge elicited a typical regulatory volume decrease (RVD). No
regulatory volume increase (RVI) was observed upon restoring
isosmotic conditions. During a second, subsequent hyposmotic
challenge, the cells did not respond with RVD. High extracellular K+
concentration and the K+ channel blockers (Ba2+ and quinine)
inhibited the RVD. RVD was abolished after replacing Cl- by gluconate
and by the Cl- channel blocker NPPB (5-nitro-2(3-phenylpropylamino)
benzoic acid). Amino acid (AA) concentration in cell and perfusate
were determined. In control, cell content amounted only 26 mmol/l.
Hypotonicity increased the efflux of AA from 0.14 to 0.60 mmol/min.
During the second hyposmotic challenge the release was 0.32 mmol/min.
The data show that C6 cells adjust their volume under hyposmotic
conditions, but lose the ability to restore their volume during a
subsequent hyposmotic treatment. K+ and Cl- are the main osmolytes
involved in volume adjustment through conductive pathways. AA do not
contribute substantially to cell volume regulation.
Received 18 May 1995; accepted in final form 16 November 1995.
APS Manuscript Number C273-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95