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Microvesicles isolated from bovine posterior pituitary accumulate norepinephrine
Y Moriyama1, A Yamamoto, H Yamada
1Department of Biochemistry and Organic Chemistry, Osaka University.
The Journal of Biological Chemistry
|May 12, 1995
Summary
Posterior pituitary microvesicles (MVs) store monoamines, identified by synaptophysin and proton-ATPase activity. These MVs facilitate norepinephrine uptake, revealing their crucial role in posterior pituitary function.
Area of Science:
- Neurobiology
- Cell Biology
- Biochemistry
Background:
- Posterior pituitary contains microvesicles (MVs).
- MVs are associated with synaptophysin, a synaptic vesicle marker.
- The function of these MVs was previously unclear.
Purpose of the Study:
- To purify and characterize MVs from the posterior pituitary.
- To identify the molecular components and enzymatic activities of these MVs.
- To determine the functional role of MVs in monoamine storage and transport.
Main Methods:
- Purification of MVs using differential and sucrose density gradient centrifugation.
- Immunoelectron microscopy to confirm synaptophysin association.
- Biochemical assays to detect ATPase activity and neurotransmitter uptake.
Main Results:
- Purified MVs (approx. 60 nm) contained synaptophysin.
- MVs exhibited bafilomycin A1-sensitive (vacuolar H+-ATPase) and vanadate-sensitive (P-ATPase) activity.
- MVs demonstrated ATP-dependent, reserpine-sensitive norepinephrine uptake, indicating a coupled monoamine transporter.
Conclusions:
- Posterior pituitary MVs are organelles responsible for monoamine storage.
- The identified vacuolar H+-ATPase drives secondary active transport of monoamines.
- This study elucidates a key mechanism for posterior pituitary neuroendocrine function.