Z. Hartley et Jm. Dubinsky, CHANGES IN INTRACELLULAR PH ASSOCIATED WITH GLUTAMATE EXCITOTOXICITY, The Journal of neuroscience, 13(11), 1993, pp. 4690-4699
Excitotoxic neuronal injury is known to be associated with increases i
n cytosolic calcium ion concentrations. However, it is not known if pe
rturbations in other intracellular ions are also associated with gluta
mate (GLU)-induced neuronal death. Accordingly, intracellular hydrogen
ion concentrations were measured in cultured hippocampal neurons with
the fluorescent dye BCECF during and after toxic exposures. Five minu
te GLU applications produced an initial cytosolic acidification. Durin
g the hour after GLU removal, intracellular pH (pH(i)) recovered stead
ily, resulting in a rebound cytosolic alkalinization. Lowering extrace
llular calcium depressed the initial GLU-induced acidification, sugges
ting that the rapid acidification may result partly as a consequence o
f calcium entry. An acidification-induced rebound alkalinization appea
red to be activated by GLU exposure. Inhibitors of intracellular pH re
gulation, harmaline, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic aci
d (DIDS), and replacement of external Na+ with N-methyl-glucamine+ (NM
G+), retarded the rate of recovery from GLU-induced acidification. The
rapid acidification and rebound alkalinization could be mimicked by c
hallenging neurons with elevated external K+ or replacement of externa
l Na+ with NMG+. Two or more hours following toxic GLU exposure, hydro
gen ion concentration did not stabilize at initial levels but progress
ively increased. High K+ or Na+ removal did not produce this long-term
acidification and were not toxic. The cumulative increase in intracel
lular hydrogen ion may reflect the declining health of injured neurons
and could contribute directly to neuronal death. Therefore, cytosolic
acidification may act synergistically with increases in calcium conce
ntration in mediating excitotoxicity.