title: PET imaging of the gastrointestinal absorption of orally administered drugs in conscious and anesthetized rats.
abstract: This study assessed the process of gastrointestinal drug absorption in vivo using PET.
  
  
  METHODS
  (18)F-FDG was used as a model probe and was orally administered to rats as a solution. PET scans were obtained of the whole body and abdominal region under conscious and anesthetized conditions. Blood samples were routinely taken from the femoral vein during scanning. The rate of gastric emptying and intestinal absorption of (18)F-FDG was estimated from the time profiles of radioactivity in the stomach and small intestine. In addition, nonradiolabeled 2-fluoro-2-deoxy-D-glucose (2-FDG) was used in an intestinal closed-loop experiment to compare the intestinal permeability of 2-FDG with that of D-glucose.
  
  
  RESULTS
  In conscious rats, gastrointestinal absorption of (18)F-FDG was rate-limited by the process of intestinal membrane permeation, because the permeability of 2-FDG through the intestinal membrane was low compared with that of d-glucose. In anesthetized rats, the gastric emptying rate of (18)F-FDG decreased dramatically whereas the intestinal absorption rate constant was not significantly different from that in conscious rats. As a result, the rate-limiting step of gastrointestinal absorption of (18)F-FDG was shifted to the gastric emptying process by anesthesia.
  
  
  CONCLUSIONS
  PET technology is a powerful tool for in vivo analysis of the gastrointestinal absorption of orally administered drugs.
authors.affiliation: Faculty of Pharmaceutical Sciences, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka, Japan. shinji@pharm.setsunan.ac.jp
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamashita
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Takashima
authors.forename: Makoto
authors.initials: M
authors.lastname: Kataoka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oh
authors.forename: Shinji
authors.initials: S
authors.lastname: Sakuma
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takahashi
authors.forename: Norio
authors.initials: N
authors.lastname: Suzuki
authors.forename: Emi
authors.initials: E
authors.lastname: Hayashinaka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Wada
authors.forename: Yilong
authors.initials: Y
authors.lastname: Cui
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000465:Algorithms; D000758:Anesthesia; D000818:Animals; D003243:Consciousness / Q000502:physiology*; D019788:Fluorodeoxyglucose F18 / Q000097:blood / Q000493:pharmacokinetics; D005746:Gastric Emptying / Q000502:physiology; D005753:Gastric Mucosa / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000000981:diagnostic imaging*; D008297:Male; D010539:Permeability; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000097:blood / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013270:Stomach / Q000000981:diagnostic imaging*
chemical_list: D004364:Pharmaceutical Preparations; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18