Intense Furosemide-Sensitive Potassium Accumulation in Astrocytes in the Presence of Pathologically High Extracellular Potassium Levels

Abstract

An intense K+ accumulation in primary cultures of astrocytes, occurring when external K+ was increased from 5.4 to 54 m M, was investigated. This increase resulted in a doubling of the K+ content within 10 s. Thirty percent of the accumulation was inhibited by furosemide (2 m M). This drug had no effect on the unidirectional influx of K+ at 5.4 m M K+, but when the extracellular K+ concentration was increased, there appeared to be a furosemide-sensitive component of the influx. This component increased with increasing external K+ levels, reaching 44% of the total influx at 72 m M. These results show that astrocytes exhibit an intense furosemide-sensitive K+ accumulation which is activated by K+ levels resembling those occurring in the extracellular compartment during pathological events. Previous studies on a furosemide-sensitive Cl− pump in cultured astrocytes suggest that this accumulation might be via KCl cotransport, which in other systems is involved in volume control.