title: Dynamic analysis of fluid distribution in the gastrointestinal tract in rats: positron emission tomography imaging after oral administration of nonabsorbable marker, [(18)F]Deoxyfluoropoly(ethylene glycol).
abstract: To develop potent drugs for oral use, information on their pharmacokinetic (PK) properties after oral administration is of great importance. We have recently reported the utility of positron emission tomography (PET) for the analysis of gastrointestinal (GI) absorption of radiolabeled compounds. In this study, PET image analysis was performed in rats using a novel PET probe, [(18)F]deoxyfluoropoly(ethylene glycol)s, with an average molecular weight of 2 kDa ([(18)F]FPEG), as a nonabsorbable marker to elaborate the GI physiology in more detail, such as segmental transition of the administered water, and fluid volume and distribution in the intestine. After oral administration of [(18)F]FPEG solution to rats, a 90 min PET scan with continuous blood sampling was performed, and then the disposition of radioactivity in each part of GI tract was investigated. From blood PK analysis, it was confirmed that the bioavailability of [(18)F]FPEG was quite low in rats. PET image analysis showed that the radioactivity after oral administration of [(18)F]FPEG solution rapidly passed through the stomach, spread into the proximal small intestine, and then transited toward the distal region of the small intestine without decreasing the radioactivity during GI transition. Radiometabolite analysis revealed that the radioactivity in intestinal mucosal tissues, blood, and urine was mainly derived from unchanged [(18)F]FPEG. It was also found that the volume of interest (VOI) after oral administration of the radiotracer enables an understanding of the time-dependent manner of effective fluid volume changes in the stomach and the small intestine. In addition, the rate constant of the intestinal transition of radioactivity in each intestinal segment was calculated by kinetic model analysis, which revealed that PET analysis enables us to determine the GI transit from the same individuals and that it is applicable to determine site-specific intestinal absorption. In conclusion, we demonstrated the high potency of PET imaging technique to elucidate the distribution of orally administered solution in the GI tract in vivo.
authors.affiliation: RIKEN Center for Molecular Imaging Science, 6-7-3 Minatojima-Minamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan. ttakashima@riken.jp
authors.forename: Tadayuki
authors.initials: T
authors.lastname: Takashima
authors.forename: Tomotaka
authors.initials: T
authors.lastname: Shingaki
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Katayama
authors.forename: Emi
authors.initials: E
authors.lastname: Hayashinaka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Wada
authors.forename: Makoto
authors.initials: M
authors.lastname: Kataoka
authors.forename: Daiki
authors.initials: D
authors.lastname: Ozaki
authors.forename: Hisashi
authors.initials: H
authors.lastname: Doi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Sho
authors.initials: S
authors.lastname: Ishida
authors.forename: Kentaro
authors.initials: K
authors.lastname: Hatanaka
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sugiyama
authors.forename: Shuji
authors.initials: S
authors.lastname: Akai
authors.forename: Naoto
authors.initials: N
authors.lastname: Oku
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamashita
authors.forename: Yasuyoshi
authors.initials: Y
authors.lastname: Watanabe
mesh_terms: D000284:Administration, Oral; D000818:Animals; D019855:Ethylene Glycol / Q000737:chemistry*; D041981:Gastrointestinal Tract / Q000378:metabolism*; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D019855:Ethylene Glycol