Measurements of mitochondrial pH in cultured cortical neurons clarify contribution of mitochondrial pore to the mechanism of glutamate-induced delayed Ca2+ deregulation.
To clarify the role of the mitochondrial permeability transition pore (MPT) in the mechanism of the glutamate-induced delayed calcium deregulation (DCD) and mitochondrial depolarization (MD), we studied changes in cytosolic (pH(c)) and mitochondrial pH (pH(m)) induced by glutamate in cultured cortical neurons expressing pH-sensitive fluorescent proteins. We found that DCD and MD were associated with a prominent pH(m) decrease which presumably resulted from MPT opening. This pH(m) decrease occurred with some delay after the onset of DCD and MD. This argued against the hypothesis that MPT opening plays a dominant role in triggering of DCD. This conclusion was also supported by experiments in which Ca(2+) was replaced with antagonist of MPT opening Sr(2+). We found that in Sr(2+)-containing medium glutamate-induced delayed strontium deregulation (DSD), similar to DCD, which was accompanied by a profound MD. Analysis of the changes in pH(c) and pH(m) associated with DSD led us to conclude that MD in Sr(2+)-containing medium occurred without involvement of the pore. In contrast, in Ca(2+)-containing medium such "non-pore mechanism" was responsible only for MD initiation while in the final stages of MD development the MPT played a major role.
Institute of General Pathology and Pathophysiology RAMS, Baltiiskaya Street 8a, Moscow, Russia.
Alexey P
AP
Bolshakov
Maria M
MM
Mikhailova
György
G
Szabadkai
Vsevolod G
VG
Pinelis
Nickolay
N
Brustovetsky
Rosario
R
Rizzuto
Boris I
BI
Khodorov
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005456:Fluorescent Dyes; D018698:Glutamic Acid / Q000378:metabolism* / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013324:Strontium / Q000494:pharmacology; D013997:Time Factors; D050994:Voltage-Dependent Anion Channels / Q000187:drug effects / Q000378:metabolism*
D005456:Fluorescent Dyes; D050994:Voltage-Dependent Anion Channels; D018698:Glutamic Acid; D002118:Calcium; D013324:Strontium