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Aspartate transport in synaptosomes from rat brain.
The Journal of Biological Chemistry
|August 10, 1983
Summary
Neuronal synapses actively transport aspartate using a mechanism coupled to electrical potential and sodium ions. This process involves the uptake of aspartate with a net charge of +2, along with protons and sodium ions.
Area of Science:
- Neuroscience
- Neurochemistry
- Molecular Biology
Background:
- Aspartate is a key neurotransmitter in the central nervous system.
- Understanding aspartate transport is crucial for synaptic function and neurological health.
Purpose of the Study:
- To elucidate the mechanism and stoichiometry of active aspartate transport in rat forebrain synaptosomes.
- To investigate the role of transmembrane electrical potential and ion gradients in aspartate uptake.
Main Methods:
- Utilized rat forebrain synaptosomes to study aspartate transport.
- Measured accumulation of labeled D-aspartate under varying ion gradients.
- Analyzed intra- and extrasynaptosomal aspartate pools and their exchange rates.
Main Results:
- Aspartate transport is driven by the electrical potential (charge +2) and coupled to the inward transport of two sodium ions.
- Identified two intrasynaptosomal aspartate pools: one Na+/K+-dependent and a slowly exchanging pool.
- Observed external medium alkalinization, suggesting proton co-transport.
Conclusions:
- The active transport of aspartate involves the co-transport of one proton and two sodium ions per aspartate molecule.
- This stoichiometry explains the energetics of both in vitro and in vivo aspartate uptake.
- The findings provide insights into the high-affinity, ion-dependent system governing aspartate neurotransmission.