Characterization of (14)C-acetate uptake in cultured rat astrocytes.

To investigate the regulation mechanism of (14)C-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 (14)C-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 alpha-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 (14)C-acetate uptake was observed with 0.5 mM fluorocitrate treatment, which indicated (14)C-acetate uptake in this study might reflect not only the transport process, but also the metabolic process. Glutamate significantly increased (14)C-acetate uptake. An increase in extracellular potassium concentration had no effect on (14)C-acetate uptake. The Ca(2+) ionophore A23187 caused a 40% reduction, and ouabain (inhibitor of Na(+)-K(+)-ATPase) and monensin (Na(+) ionophore) significantly decreased (14)C-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 Ca(2+) and Na(+) concentrations might have important roles in regulation of (14)C-acetate uptake in cultured rat astrocytes.