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[Interaction of thiamine with rat brain synaptosomes]
Z S Protasova1, Iu M Parkhomenko, G V Donchenko
1A.V. Palladin Institute of Biochemistry of Ukraine NAS, Kyiv.
Ukrains'Kyi Biokhimichnyi Zhurnal (1999 )
|May 3, 2000
Summary
This study shows that thiamine (vitamin B1) is specifically bound and transported into nerve endings. Its uptake is influenced by metabolic factors, ions, and certain neurotoxins, suggesting a link to its internal processing.
Area of Science:
- Neuroscience
- Biochemistry
Background:
- Thiamine (vitamin B1) is essential for neuronal function.
- Understanding thiamine transport mechanisms is crucial for neurological health.
Purpose of the Study:
- To investigate the specific binding and transport of thiamine into nerve endings (synaptosomes).
- To elucidate the factors influencing thiamine uptake and its relationship with intracellular processes.
Main Methods:
- Studied thiamine binding and transport kinetics in isolated synaptosomes.
- Assessed the impact of metabolic inhibitors, ions (Mg2+, Ca2+), and neurotoxins (ouabain, latrotoxin, veratridin, tetrodotoxin) on thiamine uptake.
- Examined thiamine binding under conditions of synaptic membrane depolarization.
Main Results:
- Determined apparent K[symbol: see text] and Km values for thiamine binding (2.34 ± 0.55 μM) and transport (3.92 ± 1.3 μM).
- Thiamine uptake was reduced by metabolic inhibitors and partially dependent on Mg2+ and Ca2+ ions.
- Binding was inhibited by ouabain, latrotoxin, and veratridin; tetrodotoxin showed minimal effect.
- Synaptic membrane depolarization decreased thiamine binding and promoted its efflux.
Conclusions:
- Thiamine transport into nerve endings is a specific, carrier-mediated process.
- Thiamine uptake is linked to its intracellular phosphorylation and influenced by membrane potential.
- Specific neurotoxins can interfere with thiamine transport mechanisms.