Use of mitochondrial inhibitors to differentiate kinetic properties of the ATP-dependent Ca2+ uptake system in synaptic membranes

Synaptosomal membranes accumulate 3-6 times more Ca2+ in the presence of ATP (50-1000 microM) than basal Ca2+ accumulation (-ATP). The location of this Ca2+ accumulation appears to reside on the cytosolic face of the synaptosome since lysed synaptosomes accumulate 4-times more Ca2+ than intact synap...

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Bibliographic Details
Published in:Neurochemical research 1985-02, Vol.10 (2), p.269-282
Main Authors: ROSS, D. H, GARRETT, K. N, LEE CARDENAS, H
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - pharmacology
Animals
Azides - pharmacology
Biological and medical sciences
Brain - metabolism
Calcium - metabolism
Cell Membrane Permeability
Cell physiology
Dinitrophenols - pharmacology
Fundamental and applied biological sciences. Psychology
In Vitro Techniques
Kinetics
Male
Membrane and intracellular transports
Molecular and cellular biology
Oligomycins - pharmacology
Rats
Rats, Inbred Strains
Sodium Azide
Synaptic Membranes - metabolism
Synaptosomes - metabolism
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Summary:Synaptosomal membranes accumulate 3-6 times more Ca2+ in the presence of ATP (50-1000 microM) than basal Ca2+ accumulation (-ATP). The location of this Ca2+ accumulation appears to reside on the cytosolic face of the synaptosome since lysed synaptosomes accumulate 4-times more Ca2+ than intact synaptosomes. The inclusion of mitochondrial inhibitors, oligomycin (0.7 micrograms/ml), sodium azide (100 microM) and dinitrophenol (100 microM) differentiate mitochondrial from nonmitochondrial Ca2+ accumulation under conditions that are [Ca2+]- and ATP-dependent. In the presence of low concentrations of ATP (less than 150 microM) and Ca2+ free (2.5 or 6.8 microM), Ca2+ accumulation occurs as one process in both lysed synaptosomal membranes and purified synaptic plasma membranes in the presence and/or absence of MI. When ATP levels are increased (greater than 200 microM), Ca2+ accumulation process remains independent of the presence of mitochondrial inhibitors when Ca2+ free = 2.5 microM. When Ca2+ free is increased to 6.8 microM, mitochondrial inhibitors differentiate mitochondrial from nonmitochondrial accumulation. These studies suggest that optimal conditions for the measurement of Ca2+ accumulating mechanisms in synaptosomal membranes depend on both [Ca2+] and ATP. Use of these assay conditions provide evidence that ATP-dependent Ca2+ uptake may be a viable mechanism for the regulation of synaptosomal Ca2+ levels.
ISSN:0364-3190
1573-6903
DOI:10.1007/BF00964573