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Polyamine uptake, binding and release in rat brain.
1Neuropsychiatry Branch, NIMH Neuroscience Center, Saint Elizabeths Hospital, Washington, DC 20032.
European Journal of Pharmacology
|January 25, 1991
Summary
Rat synaptosomes actively transport putrescine but bind spermidine and spermine. Polyamines are released and binding inhibited by high potassium, with binding occurring on inner membranes.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Polyamines like putrescine, spermidine, and spermine are crucial for cellular functions.
- Their roles in neuronal cells, particularly in synaptosomes, are not fully understood.
- Understanding polyamine transport and binding is key to neuronal function and dysfunction.
Purpose of the Study:
- To investigate the uptake, binding, and release mechanisms of putrescine, spermidine, and spermine in rat hippocampal synaptosomes.
- To characterize the affinity and capacity of these processes.
- To determine the localization of polyamine binding sites within synaptosomes.
Main Methods:
- Utilized synaptosomal preparations from rat hippocampus.
- Measured the uptake of radiolabeled polyamines under varying conditions.
- Assessed polyamine binding to isolated membranes.
- Investigated the effect of high potassium concentrations on uptake, binding, and release.
Main Results:
- Specific, high-affinity uptake was observed only for putrescine (Km = 28.6 nM).
- Specific binding to membranes occurred for spermidine and spermine, but not putrescine.
- High potassium induced polyamine release and inhibited binding.
- Polyamine binding was localized to the inner synaptosomal membranes.
Conclusions:
- Rat hippocampal synaptosomes exhibit selective uptake of putrescine.
- Spermidine and spermine bind to inner synaptosomal membranes, suggesting distinct roles from putrescine.
- Neuronal activity (high potassium) modulates polyamine handling, impacting release and binding.