title: Immunohistochemical localization of aquaporin-4 in the rat pituitary gland.
abstract: Aquaporin-4 (AQP4) is an isoform of membrane water channel aquaporins. It is most abundant in the brain, and is believed to be expressed by astrocytes and ependymal cells. We have reported previously that rat pituitary glands express some aquaporin subtypes, including AQP4, but the precise distribution of AQP4 in the pituitary gland is not known. The present work investigated whether AQP4 immunoreactivity exists in various pituitary cell types in adult rats, using double immunofluorescent staining and confocal microscopy. In the adenohypophysis, co-labeling for S-100 protein indicated that folliculo-stellate (FS) cells and marginal layer cells in Rathke's residual pouch have extensive labeling for AQP4. Some AQP4-expressing cells also contained glial fibrillary acidic protein (GFAP) in parenchymal tissue of the anterior lobe, and cytokeratin in marginal layer cells. AQP4 was not coexpressed in any hormone-producing pituitary cells, however. In the neurohypophysis, AQP4 was expressed in some pituicytes, which have been identified as GFAP-positive. These results suggest that AQP4, which is expressed in FS cells, in marginal layer cells and in pituicytes, but not in hormone-producing cells, is important in water transfer within the pituitary gland; astrocytes and ependymal cells do the same in the brain.
authors.affiliation: Department of Anatomy and Cell Biology, Hyogo College of Medicine, Mukogawa-cho, Nishinomiya, Hyogo, Japan. sachik@hyo-med.ac.jp
authors.forename: Sachi
authors.initials: S
authors.lastname: Kuwahara
authors.forename: Seishi
authors.initials: S
authors.lastname: Maeda
authors.forename: Yona
authors.initials: Y
authors.lastname: Ardiles
authors.forename: Jin Gon
authors.initials: JG
authors.lastname: Jun
authors.forename: Koichi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Tetsu
authors.initials: T
authors.lastname: Hayakawa
authors.forename: Makoto
authors.initials: M
authors.lastname: Seki
mesh_terms: D000818:Animals; D051401:Aquaporin 4 / Q000032:analysis*; D015415:Biomarkers / Q000032:analysis; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D018613:Microscopy, Confocal; D010902:Pituitary Gland / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D009418:S100 Proteins / Q000032:analysis
chemical_list: D051401:Aquaporin 4; D015415:Biomarkers; D005904:Glial Fibrillary Acidic Protein; D009418:S100 Proteins