Influence of isolation media on synaptosomal properties: Intracellular pH, pCa, and Ca sup 2+ uptake

Journal Article · Thu Mar 01 04:00:00 EST 1990 · Neurochemical Research; (USA)

DOI:https://doi.org/10.1007/BF00968678· OSTI ID:6644104

Bandeira-Duarte, C; Carvalho, C A; Cragoe, Junior, E J; Carvalho, A P ^[1]

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1. Univ. of Coimbra (Portugal)

Preparations of synaptosomes isolated in sucrose or in Na(+)-rich media were compared with respect to internal pH (pHi), internal Ca{sup 2+} concentration ((Ca{sup 2+})i), membrane potential and {sup 45}Ca{sup 2+} uptake due to K+ depolarization and Na{sup +}/Ca{sup 2+} exchange. We found that synaptosomes isolated in sucrose media have a pHi of 6.77 +/- 0.04 and a (Ca{sup 2+})i of about 260 nM, whereas synaptosomes isolated in Na(+)-rich ionic media have a pHi of 6.96 +/- 0.07 and a (Ca{sup 2+})i of 463 nM, but both types of preparations have similar membrane potentials of about -50 mV when placed in choline media. The sucrose preparation takes up Ca{sup 2+} only by voltage sensitive calcium channels (VSCC'S) when K(+)-depolarized, while the Na(+)-rich synaptosomes take up {sup 45}Ca{sup 2+} both by VSCC'S and by Na{sup +}/Ca{sup 2+} exchange. The amiloride derivative 2',4'-dimethylbenzamil (DMB), at 30 microM, inhibits both mechanisms of Ca{sup 2+} influx, but 5-(N-4-chlorobenzyl)-2',4' dimethylbenzamil (CBZ-DMB), at 30 microM, inhibits the Ca{sup 2+} uptake by VSCC'S, but not by Na+/Ca2+ exchange. Thus, DMB and CBZ-DMB permit distinguishing between Ca{sup 2+} flux through channels and through Na{sup +}/Ca{sup 2+} exchange. We point out that the different properties of the two types of synaptosomes studied account for some of the discrepancies in results reported in the literature for studies of Ca{sup 2+} fluxes and neurotransmitter release by different types of preparations of synaptosomes.

• OSTI ID: 6644104
• Journal Information: Neurochemical Research; (USA), Journal Name: Neurochemical Research; (USA) Vol. 15:3; ISSN 0364-3190; ISSN NERED
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
ALKALI METAL COMPOUNDS
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOELECTRICITY
BIOLOGICAL EFFECTS
BODY
BRAIN
CALCIUM 45
CALCIUM COMPOUNDS
CALCIUM ISOTOPES
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
CHEMICAL PROPERTIES
CULTURE MEDIA
DAYS LIVING RADIOISOTOPES
ELECTRICITY
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
ION EXCHANGE
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
NERVE CELLS
NERVOUS SYSTEM
NUCLEI
ORGANIC COMPOUNDS
ORGANS
PH VALUE
POTASSIUM COMPOUNDS
PROTEINS
RADIOISOTOPES
RATS
RODENTS
SODIUM COMPOUNDS
SOMATIC CELLS
TRACER TECHNIQUES
UPTAKE
VERTEBRATES