EFFECT OF HYPERTHERMIA ON INTRACELLULAR PH IN HUMAN U-87 MG GLIOBLASTOMA CELLS

The effect of hyperthermia at 43 degrees C on intracellular pH (pH(i)) in human U-87 MG glioblastoma cells was studied by using the fluoresc ent probe yethyl)-5(6)-carboxyfluorescein-pentaacetoxymethyl ester. Th e presence of Na+/H+ antiporter activity in the cells were demonstrate d by the Na+-dependent increase in intracellular pH (pH(i)) after cell ular acidification in the absence of HCO3-. Hyperthermia at 43 degrees C caused significant decrease in pH(i). The acidification was readily reversible by cooling the cells back down to 37 degrees C. The pH(i) change was inhibited by the addition of 1 mM amiloride in the incubati on medium. Amiloride and hyperthermia exhibited a synergistic effect i n suppressing thymidine incorporation into the cells.