IMPAIRED CELL-VOLUME REGULATION IN TAURINE DEFICIENT CULTURED ASTROCYTES

Taurine concentration was reduced by 40 and 65%, respectively in rat c erebellar astrocytes grown in a chemically defined medium or in cultur e medium containing a blocker of taurine transport (GES). Cell volume in these taurine deficient cells was 10%-16% higher than in controls. When challenged by hyposmotic conditions, astrocytes release taurine a nd this efflux contributes to the volume regulatory decrease observed in these cells. Taurine deficient astrocytes showed a less efficient v olume recovery as compared to controls with normal taurine levels. Exp osed to 50% hyposmotic medium, astrocytes with normal taurine concentr ation recovered 60% of their original volume whereas taurine deficient cells recovered only 30-35%. Similarly, in 30% hyposmotic medium, tau rine deficient astrocytes recovered only 40% as compared to 75% in con trols, No compensatory increases in the efflux of other osmolytes (fre e amino acids or potassium) were observed during regulatory volume dec rease in taurine deficient astrocytes.