A reevaluation of the role of mitochondria in neuronal Ca2+ homeostasis

• Published in: Journal of neurochemistry Vol. 66; no. 1; p. 403
• Main Authors: Budd, S L, Nicholls, D G
• Format: Journal Article
• Language: English
• Published: England 01.01.1996
• Subjects: Adenosine Triphosphate - physiology; Animals; Biological Transport, Active - drug effects; Calcium - metabolism; Carbonyl Cyanide m-Chlorophenyl Hydrazone - pharmacology; Cerebellum - cytology; Cerebellum - drug effects; Cerebellum - metabolism; Energy Metabolism - drug effects; Homeostasis - drug effects; Ionophores - pharmacology; Membrane Potentials - drug effects; Mitochondria - drug effects; Mitochondria - physiology; Neurons - drug effects; Neurons - metabolism; Neurons - ultrastructure; Oligomycins - pharmacology; Potassium Chloride - pharmacology; Protons; Rats; Rats, Wistar; Uncoupling Agents - pharmacology
• ISSN: 0022-3042
• DOI: 10.1046/j.1471-4159.1996.66010403.x

The ability of mitochondrial Ca2+ transport to limit the elevation in free cytoplasmic Ca2+ concentration in neurones following an imposed Ca2+ load is reexamined. Cultured cerebellar granule cells were monitored by digital fura-2 imaging. Following KCl depolarization, addition of the protonophore carbonylcyanide m-chlorophenylhydrazone (CCCP) to depolarize mitochondria released a pool of Ca2+ into the cytoplasm in both somata and neurites. No CCCP-releasable pool was found in nondepolarized cells. Although the KCl-evoked somatic and neurite Ca2+ concentration elevations were enhanced when CCCP was present during KCl depolarization, this was associated with a collapsed ATP/ADP ratio. In the presence of the ATP synthase inhibitor oligomycin, glycolysis maintained high ATP/ADP ratios for at least 10 min. The further addition of the mitochondrial complex I inhibitor rotenone led to a collapse of the mitochondrial membrane potential, monitored by rhodamine-123, but had no effect on ATP/ADP ratios. In the presence of rotenone/oligomycin, no CCCP-releasable pool was found subsequent to KCl depolarization, consistent with the abolition of mitochondrial Ca2+ transport; however, paradoxically the KCl-evoked Ca2+ elevation is decreased. It is concluded that the CCCP-induced increase in cytoplasmic Ca2+ response to KCl is due to inhibition of nonmitochondrial ATP-dependent transport and that mitochondrial Ca2+ transport enhances entry of Ca2+, perhaps by removing the cation from cytoplasmic sites responsible for feedback inhibition of voltage-activated Ca2+ channel activity.