Characterization of 14C-acetate uptake in cultured rat astrocytes

To investigate the regulation mechanism of 14C-acetate uptake in astrocytes, uptake experiments with cultured rat astrocytes were performed. In this study, we used a relatively low concentration (0.0185 mM) of 14C-acetate. The uptake was dependent on pH and acetate concentration, and saturated by 10 mM acetate. Furthermore, the selective inhibition by p-(chloromercuri) benzenesulfonic acid (pCMBS) but not by α-cyano-3-hydroxycinnamate (CHC) showed that the monocarboxylate transporter-1 (MCT-1)-mediated transport system is essentially important in cultured rat astrocytes. A significant reduction (more than 30%) in 14C-acetate uptake was observed with 0.5 mM fluorocitrate treatment, which indicated 14C-acetate uptake in this study might reflect not only the transport process, but also the metabolic process. Glutamate significantly increased 14C-acetate uptake. An increase in extracellular potassium concentration had no effect on 14C-acetate uptake. The Ca2+ ionophore A23187 caused a 40% reduction, and ouabain (inhibitor of Na+-K+-ATPase) and monensin (Na+ ionophore) significantly decreased 14C-acetate uptake by astrocytes. The combined use of ouabain and monensin caused significantly greater decreases than the addition of either chemical alone. These results suggest that glutamate stimulation and changes in Ca2+ and Na+ concentrations might have important roles in regulation of 14C-acetate uptake in cultured rat astrocytes.