IONIC MECHANISMS IN GLUTAMATE-INDUCED ASTROCYTE SWELLING - ROLE OF K+INFLUX

L-Glutamate (L-GLU) induced astrocyte swelling in a time-and concentra tion-dependent, as wed as Na+- and Ca2+-dependent, and Cl--independent manner. Swelling was prevented by MK-801, cystine, and ouabain, Since L-GLU swelling is ionically dependent, we determined the role of vari ous ions in such swelling. Our results indicate that K+ uptake plays a major role in the mechanism of L-GLU-induced astrocyte swelling. Like swelling, K+ uptake is dependent on Ca2+ and Na+, but not on Cl-, Lik ewise, K+ uptake was inhibited by MK-801, cystine, and ouabain, The K channel blockers, Ba2+ and tetraethylammonium, partially prevented L- GLU-induced swelling. In addition to K+ channels, K+ influx may also b e mediated through Na+/K+-ATPase, as its activity is increased by L-GL U uptake along with the required Na+. Taken together, the data suggest that K+ influx plays a key role in the mechanism of L-GLU-mediated as trocyte swelling. (C) 1998 Wiley-Liss, Inc.