Extracellular hydrogen ions influence channel-mediated and carrier-mediated K+ fluxes in cultured mouse astrocytes.

Physiological (pH 7.2 and 7.0) and pathological (pH 6.8 and 6.6) changes of external pH, as they are measured in vivo, were imposed on mouse astrocytes in primary cultures and the effect on components of K+ transport pathways across the cell membrane was measured. Physiological pH changes had no effect at all. Pathological pH changes in inhibited K+ fluxes through channels by 40%. This effect occurred 3-6 min after a pH change and was not additive to a similar change induced by amiloride. This could be seen as an indication that the observed effects are mediated by subsequent changes in intracellular pH; however, direct intracellular pH measurements were not undertaken. A low pH of 6.6 inhibited the activity of the Na+, K+-ATPase by 65% and reduced the carrier-mediated K+ net accumulation into the cells by 60%. This suggests that measured extracellular pH changes in the brain may be functionally important, as they interfere with the K+ homeostasis of the nervous tissue.