Temporal association between alterations in proton extrusion and low pH adaptation

Abstract

Cells which have been adapted to growth at low extracellular pH (pH_e) typically develop both an upregulation of steady state intracellular pH (pH_i) and an ability to develop thermotolerance to 42d`C hyperthermia. These properties were acquired at different times, however. Days were required at pH_e = 6.70 for two cell lines to adapt to low pH_e by the thermotolerance criterion, but both had elevated steady state pH_i values after only 4 hours at pH_e = 6.70. A better correlation with adaptation to low pH_e (as defined by hyperthermia) was found with changes in proton extrusion and the rate of pH_i recovery after cytosolic acidification.

Key Words:

• Intracellular pH
• fluorescence
• hyperthermia
• transmembrane proton transport