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UPTAKE AND RELEASE OF 45 Ca BY BRAIN MICROSOMES, SYNAPTOSOMES AND SYNAPTIC VESICLES 1, 2
Author(s) -
Diamond I.,
Goldberg A. L.
Publication year - 1971
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1971.tb00005.x
Subject(s) - calcium , chemistry , microsome , synaptosome , synaptic vesicle , biochemistry , vesicle , choline , ouabain , sucrose , biophysics , sodium , membrane , biology , in vitro , organic chemistry
— Microsomes and synaptosomes from rat brain accumulated 4,5 Ca against a concentration gradient by an ATP‐dependent process. Calcium accumulation occurred to the same extent in microsomes prepared from white matter and from grey matter, an observation suggesting that calcium uptake may be in part an activity of the axonal membrane. Microsomes and synaptosomes accumulated calcium to a similar extent but less actively than mitochondria. By contrast, synaptic vesicles showed relatively little calcium accumulation. Isotonic concentrations of sucrose, NaCl, KCl and choline chloride inhibited calcium accumulation, with NaCl and KCl the least effective of these inhibitory agents. No consistent effects on calcium uptake were obtained with adenosine 3′,5′‐monophosphate, dibutyryl cyclic AMP or the methyl xanthines. Incubation of prelabelled microsomes resulted in a release of 45 Ca, and ATP inhibited this release process. In the absence of added ATP, isotonic NaCl promoted calcium release to a significantly greater extent than KCl choline chloride or sucrose. In the presence of ATP, these agents all promoted a similar degree of release. Adenosine 3′,5′‐monophosphate or agents that affect its metabolism did not significantly affect calcium release. Magnesium ions reduced calcium release under all conditions tested.