CHANGES IN ORGANIC SOLUTES, VOLUME, ENERGY-STATE, AND METABOLISM ASSOCIATED WITH OSMOTIC-STRESS IN A GLIAL-CELL LINE - A MULTINUCLEAR NMR-STUDY

Diffusion-weighted in vivo H-1-NMR spectroscopy of F98 glioma cells em bedded in basement membrane gel threads showed that the initial cell s welling to about 180% of the original volume induced under hypotonic s tress was followed by a regulatory volume decrease to nearly 100% of t he control volume in Dulbecco's modified Eagle's medium (DMEM) but onl y to 130% in Krebs-Henseleit buffer (KHB, containing only glucose as a substrate) after 7 h. The initial cell shrinkage to approx. 70% induc ed by the hypertonic stress was compensated by a regulatory volume inc rease which after 7 h reached almost 100% of the control value in KHB and 75% in DMEM. H-1-, C-13- and P-31-NMR spectroscopy of perchloric a cid extracts showed that these volume regulatory processes were accomp anied by pronounced changes in the content of organic osmolytes. Adapt ation of intra- to extracellular osmolarity was preferentially mediate d by a decrease in the cytosolic taurine level under hypotonic stress and by an intracellular accumulation of amino acids under hypertonic s tress. If these solutes were not available in sufficient quantities (a s in KHB), the osmolarity of the cytosol was increasingly modified by biosynthesis of products and intermediates of essential metabolic path ways, such as alanine, glutamate and glycerophosphocholine in addition to ethanolamine. The cellular nucleoside triphosphate level measured by in vivo P-31-NMR spectroscopy indicated that the energy state of th e cells was more easily sustained under hypotonic than hypertonic cond itions.