A PERSISTENT CALCIUM-DEPENDENT DECREASE O F CYTOPLASMIC PH IN CULTURED NERVE-CELLS INDUCED BY TOXIC GLUTAMATE TREATMENT

Dynamics of intracellular pH (pH(i)) during and after toxic glutamate treatment of monolayer cerebellar granule cell cultures was performed using the intracellular fluorescent probe BCECF/2AM. The exposure of c ultures for 15 min to 50 muM glutamate in Mg2+-free solution resulted in a substantial decrease in pH(i) which persisted after glutamate rem oval. Replacement of the control salt solution by Ca2+-free one contai ning 1 mM EGTA led to the increase in pH(i) sometimes almost to its in itial level. The above changes of pH(i) closely correlated with those of intracellular Ca2+ concentration ([Ca2+]i) measured in parallel exp eriments using the fluorescent probe Fura 2/AM: a decrease in pH(i) co rresponded to an increase in [Ca2+]i and vice versa. Intracellular aci dosis is known to suppress both Na0+/Ca(i)2+ exchange and Ca2+ pump. T herefore, it can be suggested that the glutamate-induced pH(i) lowerin g is one of the major reasons for an incapability of nerve cells to ex trude excess Ca2+ from the cytosol after toxic glutamate treatment.