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Vesicular Monoamine Transporter 1 Is Responsible for Storage of 5‐Hydroxytryptamine in Rat Pinealocytes
Author(s) -
Hayashi Mitsuko,
Haga Megumi,
Yatsushiro Shouki,
Yamamoto Akitsugu,
Moriyama Yoshinori
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0732538.x
Subject(s) - pinealocyte , vesicular monoamine transporter , monoamine neurotransmitter , vesicular monoamine transporter 2 , vesicle , vesicular transport protein , biology , reserpine , microbiology and biotechnology , chemistry , pineal gland , medicine , serotonin , endocrinology , biochemistry , melatonin , receptor , membrane
: Vesicular monoamine transporters (VMATs) are involved in chemical transduction in monoaminergic neurons and various endocrine cells through the storage of monoamines in secretory vesicles. Mammalian pinealocytes contain more 5‐hydroxytryptamine (5‐HT) than any other cells and are expected on contain VMAT, although no information is available so far. Upon the addition of ATP, radiolabeled 5‐HT was taken up by a particulate fraction prepared from cultured rat pinealocytes. The 5‐HT uptake was inhibited significantly by bafilomycin A 1 (an inhibitor of vacuolar H + ‐ATPase), 3,5‐di‐ tert ‐butyl‐4‐hydroxybenzyli‐denemalononitrile (a proton conductor), or reserpine (an inhibitor of VMAT). RT‐PCR analysis suggested that VMAT type 1 (VMAT1), but not type 2, is expressed. Antibodies against VMAT1 recognized a single polypeptide with an apparent molecular mass of ~55 kDa, and specifically immunostained pinealocytes. VMAT1 immunoreactivity was high in the vesicular structures in the varicosities of long branching processes and was associated with 5‐HT, but not with synaptophysin, a marker protein for microvesicles. The 5‐HT immunoreactivity in the long branching processes disappeared upon incubation with reserpine. These results indicate that 5‐HT, at least in part, is stored in vesicles other than microvesicles in pinealocytes through a mechanism similar to that of various secretory vesicles.