Immunohistochemical study of the glutamate transporter proteins GLT-1 and GLAST in rat and gerbil pineal gland.
Several investigations performed during this decade have led to the hypothesis that small secretory vesicles of pinealocytes (generally referred to as synaptic-like microvesicles, SLMVs) are components of a system for intercellular paracrine communication between pineal cells, which shares many features with the process of synaptic neurotransmission. According to a recent study, one parallel that can be drawn to synaptic signal transduction seems to be the presence of pineal re-uptake systems for messenger molecules released from SLMVs, i.e. for neuroactive amino acids such as L-glutamate. In order to further characterize these uptake mechanisms, we have carried out an immunohistochemical study to explore the presence and cellular localization of the glutamate transporters GLT-1 and GLAST in rat and gerbil pineal glands. GLT-1 and GLAST were always detected in a subpopulation of pineal parenchymal cells in both species. Using immunostaining of serial semithin sections with antibodies against marker proteins of pineal cell types, GLT-1- and GLAST-positive cells were identified as interstitial glial cells. In addition, some pinealocytes also displayed immunoreactivity for GLT-1. In contrast to current thinking, our findings show that GLT-1 is not the only glutamate transporter subtype expressed in the pineal gland. Moreover, our observations point to a significant participation of interstitial cells in the process of pineal glutamatergic communication, reminiscent of the role of glial cells during glutamatergic neurotransmission in the central nervous system.
Redecker
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P
Medizinische Hochschule Hannover, Abt. Anatomie 1, Germany. redecker.peter@mh-hannover.de
Pabst
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H
D018528:ATP-Binding Cassette Transporters / Q000032:analysis*; D000595:Amino Acid Sequence; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001692:Biological Transport; D005260:Female; D005849:Gerbillinae; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D018698:Glutamic Acid / Q000032:analysis*; D007124:Immunoenzyme Techniques; D008297:Male; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000737:chemistry; D010446:Peptide Fragments / Q000276:immunology; D010870:Pineal Gland / Q000737:chemistry* / Q000166:cytology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D016708:Synaptophysin / Q000032:analysis; D014746:Vimentin / Q000032:analysis
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D005904:Glial Fibrillary Acidic Protein; D010446:Peptide Fragments; D016708:Synaptophysin; D014746:Vimentin; D018698:Glutamic Acid