title: Origin of posterior pituitary high intensity on T1-weighted magnetic resonance imaging. Immunohistochemical, electron microscopic, and magnetic resonance studies of posterior pituitary lobe of dehydrated rabbits.
abstract: OBJECTIVE
  To investigate the origin of posterior pituitary high intensity (PPHI) seen on T1-weighted magnetic resonance (MR) images.
  
  
  METHODS
  Six rabbits, including four rabbits deprived of drinking water for 4 days and two control rabbits, were examined by MR imaging. Plasma vasopressin levels were sequentially measured by radioimmunoassay. Pituitary glands were immunostained with guinea pig anti-rabbit vasopressin antibody, and ultrathin sections of Epon/Araldite-embedded specimens were observed with a transmission electron microscope.
  
  
  RESULTS
  In control rabbits, PPHI was noted on T1-weighted MR images, and the posterior pituitary lobe was positively immunostained with anti-vasopressin antibody. At the ultrastructural level, nerve terminals contained numerous neurosecretory granules bearing vasopressin. Conversely, plasma vasopressin levels gradually increased and PPHI was absent in 4-day dehydrated rabbits. The posterior lobe was scarcely stained with anti-vasopressin antibody, and neurosecretory granules were rarely observed. However, a number of small dispersed vesicles, possibly derived from the fragmentation of neurosecretory granule envelopes, were seen in the nerve terminal.
  
  
  CONCLUSIONS
  Posterior pituitary high signal seen on T1-weighted MR images is attributed to neurosecretory granules bearing vasopressin.
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Gunma University, Maebashi, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Sato
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.forename: M
authors.initials: M
authors.lastname: Tateno
authors.forename: N
authors.initials: N
authors.lastname: Ohya
authors.forename: K
authors.initials: K
authors.lastname: Takata
authors.forename: K
authors.initials: K
authors.lastname: Endo
mesh_terms: D000818:Animals; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D003681:Dehydration / Q000097:blood / Q000473:pathology*; D004853:Epoxy Resins; D007089:Image Enhancement; D007150:Immunohistochemistry; D008279:Magnetic Resonance Imaging; D008297:Male; D008854:Microscopy, Electron; D009411:Nerve Endings / Q000648:ultrastructure; D009489:Neurosecretion; D010796:Phthalic Anhydrides; D010904:Pituitary Gland, Posterior / Q000473:pathology* / Q000648:ultrastructure; D016613:Plastic Embedding; D011817:Rabbits; D011863:Radioimmunoassay; D014667:Vasopressins / Q000032:analysis / Q000097:blood
chemical_list: D004853:Epoxy Resins; D010796:Phthalic Anhydrides; D014667:Vasopressins; C005752:araldite; C004875:EPON