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[Aggregation and swelling of brain synaptic vesicles in rats]
Summary
Magnesium-adenosine triphosphatase (Mg-ATPase) in rat brain synaptic vesicles causes swelling, mediated by proton pumps. This swelling is influenced by chloride ions and counteracted by calcium-induced aggregation.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Synaptic vesicles (SV) are crucial for neurotransmission.
- Understanding the biophysical properties of SV is essential for comprehending synaptic function.
Purpose of the Study:
- To investigate the effects of Mg-adenosine triphosphatase (Mg-ATPase) on rat brain synaptic vesicle morphology.
- To elucidate the role of proton pumps and ion permeability in SV swelling and aggregation.
Main Methods:
- Measurement of light scattering intensity (I1) at 620 nm to assess SV swelling and aggregation.
- Treatment with Mg-ATPase, proton pump inhibitors (dicyclohexylcarbodiimide, carbonylcyanide m-chlorophenylhydrazone), permeable anions (KCl), and divalent cations (Ca2+, Mg2+).
Main Results:
- Mg-ATPase (1 mM) induced SV swelling, confirmed by decreased light scattering.
- Swelling was abolished by proton pump blockers, indicating H+-ATPase involvement.
- Permeable anions like chloride enhanced Mg-ATPase-induced swelling.
- High concentrations of Ca2+ and Mg2+ caused SV aggregation.
- Mg-ATP reduced Ca2+-induced aggregation.
Conclusions:
- Mg-ATPase activity is linked to H+-ATPase-mediated SV swelling.
- Ion permeability, particularly chloride, modulates SV swelling.
- Divalent cations induce SV aggregation, while Mg-ATP can mitigate this effect.