Calcium‐Dependent and‐Independent Release of Glutamate from Synaptosomes Monitored by Continuous Fluorometry

Calcium‐Dependent and‐Independent Release of Glutamate from Synaptosomes Monitored by... Abstract: An enzyme‐linked fluorometric assay is described for the continuous monitoring of the unidirectional efflux of glutamate from guinea‐pig synaptosomes. Glutamate efflux from freshly suspended, polarized synaptosomes occurs at 0.35–0.39 nmol min−1 mg of protein−1 and is not significantly affected by external Ca2+. KC1 depolarization (30 mM KCI) in the absence of Ca2+ doubles this rate, whereas in the presence of Ca2+, the initial kinetics of the assay are consistent with the release in the first 5 s of 0.6 nmol mg of protein−1. The final extent of Ca2+‐dependent release amounts to 1.9 nmol mg of protein−1, or 8.5% of the total intrasynaptosomal glutamate content. Preincubation of synaptosomes at 30°C for 2 h before depolarization leads to a decrease in Ca2+‐independent release and an increase in Ca2+‐dependent release, consistent with an intrasynaptosomal relocation of the amino acid. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurochemistry Wiley

Calcium‐Dependent and‐Independent Release of Glutamate from Synaptosomes Monitored by Continuous Fluorometry

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Publisher
Wiley
Copyright
Copyright © 1987 Wiley Subscription Services, Inc., A Wiley Company
ISSN
0022-3042
eISSN
1471-4159
DOI
10.1111/j.1471-4159.1987.tb03393.x
Publisher site
See Article on Publisher Site

Abstract

Abstract: An enzyme‐linked fluorometric assay is described for the continuous monitoring of the unidirectional efflux of glutamate from guinea‐pig synaptosomes. Glutamate efflux from freshly suspended, polarized synaptosomes occurs at 0.35–0.39 nmol min−1 mg of protein−1 and is not significantly affected by external Ca2+. KC1 depolarization (30 mM KCI) in the absence of Ca2+ doubles this rate, whereas in the presence of Ca2+, the initial kinetics of the assay are consistent with the release in the first 5 s of 0.6 nmol mg of protein−1. The final extent of Ca2+‐dependent release amounts to 1.9 nmol mg of protein−1, or 8.5% of the total intrasynaptosomal glutamate content. Preincubation of synaptosomes at 30°C for 2 h before depolarization leads to a decrease in Ca2+‐independent release and an increase in Ca2+‐dependent release, consistent with an intrasynaptosomal relocation of the amino acid.

Journal

Journal of NeurochemistryWiley

Published: Jul 1, 1987

References

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