Dissection of mitochondrial Ca2+ uptake and release fluxes in situ after depolarization-evoked [Ca2+](i) elevations in sympathetic neurons. J Gen Physiol 2000 Mar;115(3):351-70
Date
02/29/2000Pubmed ID
10694263Pubmed Central ID
PMC2217215DOI
10.1085/jgp.115.3.351Scopus ID
2-s2.0-0034145480 (requires institutional sign-in at Scopus site) 100 CitationsAbstract
We studied how mitochondrial Ca2+ transport influences [Ca2+](i) dynamics in sympathetic neurons. Cells were treated with thapsigargin to inhibit Ca2+ accumulation by SERCA pumps and depolarized to elevate [Ca2+(i); the recovery that followed repolarization was then examined. The total Ca2+ flux responsible for the [Ca2+](i) recovery was separated into mitochondrial and nonmitochondrial components based on sensitivity to the proton ionophore FCCP, a selective inhibitor of mitochondrial Ca2+ transport in these cells. The nonmitochondrial flux, representing net Ca2+ extrusion across the plasma membrane, has a simple dependence on [Ca2+](i), while the net mitochondrial flux (J(mito)) is biphasic, indicative of Ca+) accumulation during the initial phase of recovery when [Ca2+](i) is high, and net Ca2+ release during later phases of recovery. During each phase, mitochondrial Ca2+ transport has distinct effects on recovery kinetics. J(mito) was separated into components representing mitochondrial Ca2+ uptake and release based on sensitivity to the specific mitochondrial Na(+)/Ca2+ exchange inhibitor, CGP 37157 (CGP). The CGP-resistant (uptake) component of J(mito) increases steeply with [Ca2+](i), as expected for transport by the mitochondrial uniporter. The CGP-sensitive (release) component is inhibited by lowering the intracellular Na(+) concentration and depends on both intra- and extramitochondrial Ca2+ concentration, as expected for the Na(+)/Ca2+ exchanger. Above approximately 400 nM [Ca2+](i), net mitochondrial Ca2+ transport is dominated by uptake and is largely insensitive to CGP. When [Ca2+](i) is approximately 200-300 nM, the net mitochondrial flux is small but represents the sum of much larger uptake and release fluxes that largely cancel. Thus, mitochondrial Ca2+ transport occurs in situ at much lower concentrations than previously thought, and may provide a mechanism for quantitative control of ATP production after brief or low frequency stimuli that raise [Ca(2+)](i) to levels below approximately 500 nM.
Author List
Colegrove SL, Albrecht MA, Friel DDAuthor
Meredith A. Albrecht MD, PhD Associate Professor in the Anesthesiology department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBiological Transport
Calcium
Calcium Signaling
Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone
Clonazepam
Male
Mitochondria
Neurons
Patch-Clamp Techniques
Potassium
Rana catesbeiana
Sodium
Sympathetic Nervous System
Thiazepines
Uncoupling Agents
