Isovolumetric regulation of C6 rat glioma cells in hyperosmotic media
Mountian, I.; Van Driessche, W.
American Journal of Physiology 272(1 Pt 1): C318-C323
1997
ISSN/ISBN: 0002-9513 PMID: 9038838 Document Number: 477747
Volume regulation of C6 glioma cells was studied in response to a gradual increase of extracellular osmolality from 300 to 440 mosmol/kgH-2O at 37 degree C. Maintenance of cell size depended on the rate of osmolality increase (CR); at CR of 3 mosmol cntdot kg-1 cntdot min-1, cell volume was kept constant, whereas it decreased progressively at CR of 6 or 9 mosmol cntdot kg-1 cntdot min-1. The ability of C6 cells to maintain their volume is termed isovolumetric regulation (IVR). Reducing temperature to 22 degree C inhibited IVR significantly. Also, bumetanide and ouabain blocked the regulation, while 5-(N,N-dimethyl)amiloride (DMA) did not affect IVR. Extracellular acidification rate (EAR) was studied by microphysiometry. EAR gradually decreased in the presence and increased in the absence of IVR. Experiments with DMA show that these changes in EAR were related to the activity of the Na+/H+ exchanger. It was stimulated by cell shrinkage but not by hyperosmolality itself Our data demonstrate that C6 glioma cells are able to prevent volume decrease at a low rate of elevation of external osmolality and at 37 degree C. This process requires electrolyte uptake by the Na+-K+-2Cl- cotransporter and Na+/K+ pump.