Demonstration of vesicular glutamate transporter-1 in corticotroph cells in the anterior pituitary of the rat.
Recent immunohistochemical studies of the rat adenohypophysis identified type-2 vesicular glutamate transporter (VGLUT2), a marker for glutamatergic neuronal phenotype, in high percentages of adenohypophysial gonadotrophs and thyrotrophs. The presence and molecular identity of amino acid neurotransmitters in the remaining hormone producing cell types are unknown. In the present study we addressed the putative synthesis of another glutamatergic marker, VGLUT1 by adenohypophysial cells. Immunohistochemical studies revealed VGLUT1 immunoreactivity in a small subset of polygonal medium-sized cells in the anterior lobe. Western blot analysis revealed a single major 60 kDa protein band in the adenohypophysis. Furthermore, the expression of VGLUT1 mRNA was confirmed by reverse transcription-polymerase chain reaction followed by sequence analysis of the amplicon. In contrast with rats which only showed VGLUT1 signal in the anterior lobe of the pituitary, mice contained high levels of VGLUT1 immunoreactivity in the intermediate, in addition to the anterior lobe. No signal was present in VGLUT1-knockout mice, providing evidence for specificity. In rats, results of colocalization studies with dual-immunofluorescent labeling provided evidence for VGLUT1 immunoreactivity in 45.9% of corticotrophs and 7.7% of luteinizing hormone beta-immunopositive gonadotrophs. Cells of the other peptide hormone phenotypes were devoid of VGLUT1 signal. A few cells in the adenohypophysis expressed both VGLUT1 and VGLUT2 immunoreactivities. The presence of the glutamate markers VGLUT1 and VGLUT2 in distinct populations of peptide hormone-secreting hypophysial cells highly indicates the involvement of endogenous glutamate release in autocrine/paracrine regulatory mechanisms. The biological function of adenohypophysial glutamate will require clarification.
Kocsis
Zsuzsa S
ZS
Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest 1083, Hungary.
Molnár
Csilla S
CS
Watanabe
Masahiko
M
Daneels
Guy
G
Moechars
Dieder
D
Liposits
Zsolt
Z
Hrabovszky
Erik
E
D000305:Adrenal Cortex Hormones / Q000378:metabolism; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D019898:Autocrine Communication; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D050598:Vesicular Glutamate Transport Protein 1 / Q000235:genetics / Q000378:metabolism*; D050599:Vesicular Glutamate Transport Protein 2 / Q000235:genetics / Q000378:metabolism
D000305:Adrenal Cortex Hormones; D012333:RNA, Messenger; C493475:Slc17a6 protein, rat; C493466:Slc17a7 protein, rat; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D018698:Glutamic Acid; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone