Intracellular ATP depletion inhibits swelling-induced D-[3H]aspartate release from primary astrocyte cultures

Volume expansion-sensing outward rectifier (VSOR) anion channel, also referred to as volume-sensitive organic osmolyte-anion channel (VSOAC), appears to be responsible for cell swelling-induced amino acid release in a variety of cells. One prominent feature of the VSOR/VSOAC is that non-hydrolyzed intracellular ATP binding to the channel or an accessory protein is required for its activation. In this study, the effect of intracellular ATP depletion on the swelling-induced release of D-[3H]aspartate from rat primary astrocyte cultures due to exposure to either high K(+) or hypotonic media was studied. When the cells were pretreated for 10 min with a combination of the metabolic inhibitors 2-deoxyglucose and rotenone, 100 mM K(+) media- or hypotonic media-induced D-[3H]aspartate release was completely suppressed. Added separately, each inhibitor showed only partial or no inhibition of D-[3H]aspartate release, which correlated with its relative effectiveness in decreasing intracellular ATP levels. These data are consistent with the view that during high [K(+)](o) or hypotonic media-induced swelling of primary astrocyte cultures an ATP-dependent swelling-activated VSOAC channel is responsible for D-[3H]aspartate release and close to normal ATP is required for full channel activation.