Characterization of Arsenate Uptake by Cultured Primary Rat Astrocytes

Abstract

Arsenate is known to be accumulated by cultured astrocytes and to stimulate astrocytic glutathione export, but the arsenate uptake into astrocytes has not been characterized so far. To address this topic, we have exposed primary rat astrocyte cultures to arsenate and determined the cellular arsenic content by atomic absorption spectroscopy. Viable astrocytes accumulated arsenate in a time- and concentration-dependent manner. Their cellular arsenic content increased almost proportional with time for up to 60min after application of arsenate. Analysis of the concentration-dependent increase in the specific arsenic content of the cells after 30min of arsenate exposure revealed that cultured astrocytes take up arsenate with saturable kinetics by a transport process that has apparent KM- and Vmax-values of 1.7±0.2mM and 28±4nmol/(mg protein×30min), respectively. Arsenate uptake in viable astrocytes was strongly inhibited by the presence of phosphate or by lowering the incubation temperature to 4°C and was completely abolished in a sodium ion-free medium. These results strongly suggest that the saturable temperature-dependent arsenate uptake into astrocytes is mediated by a sodium-dependent phosphate cotransporter.