title: (123)I- or (125)I-metaiodobenzylguanidine visualization of brown adipose tissue.
abstract: (123)I-Metaiodobenzylguanidine (MIBG) accumulations that do not correspond to any tumor are observed occasionally on the medial aspect of the upper back or shoulder of children. The true nature of such accumulations is unknown, and we hypothesized that they represent interscapular brown adipose tissue (IBAT) visualized by scintigraphy.
  
  
  METHODS
  Wistar rats (7 wk old) received MIBG labeled with (123)I or (125)I. Autoradiography was performed, and concentrations of the tracer in the interscapular subcutaneous tissue were identified histopathologically. The effects of 6-hydroxydopamine, reserpine, and beta 3-adrenergic receptor agonist (CL316,243) on the accumulation were investigated to elucidate the mechanism of uptake into BAT.
  
  
  RESULTS
  Autoradiography showed well-defined distinct accumulation in the subcutaneous tissue on the upper back, and hematoxylin-eosin and anti-uncoupling protein 1 antibody staining confirmed that it was BAT. The percentage injected dose per gram in BAT was as high as that in the heart and was quite different from the concentration in white adipose tissue. Preadministration of 6-hydroxydopamine or reserpine resulted in lower MIBG concentrations in BAT. Activation of the beta 3-adrenergic receptor accelerated the washout of MIBG in BAT and caused an increase in concentration in white adipose tissue.
  
  
  CONCLUSIONS
  MIBG accumulates in the adrenergic nervous system in BAT, and IBAT is distinguished from the surrounding white adipose tissue. To our knowledge, BAT has not been visualized previously. We showed that MIBG scintigraphy might be suitable for the investigation of BAT and treatment of human obesity.
authors.affiliation: Department of Radiology, Kyoto Prefectural University of Medicine, Kyoto, Japan. chio@koto.kpu-m.ac.jp
authors.forename: Chio
authors.initials: C
authors.lastname: Okuyama
authors.forename: Naoki
authors.initials: N
authors.lastname: Sakane
authors.forename: Toshihide
authors.initials: T
authors.lastname: Yoshida
authors.forename: Keiji
authors.initials: K
authors.lastname: Shima
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kurosawa
authors.forename: Kenzo
authors.initials: K
authors.lastname: Kumamoto
authors.forename: Yo
authors.initials: Y
authors.lastname: Ushijima
authors.forename: Tsunehiko
authors.initials: T
authors.lastname: Nishimura
mesh_terms: D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics; D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism; D018663:Adrenergic Agents / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D004149:Dioxoles / Q000494:pharmacology; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D016627:Oxidopamine / Q000494:pharmacology; D011877:Radionuclide Imaging; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology
chemical_list: D018663:Adrenergic Agents; D000318:Adrenergic beta-Agonists; D004149:Dioxoles; D007457:Iodine Radioisotopes; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; D019797:3-Iodobenzylguanidine; D012110:Reserpine; D016627:Oxidopamine