title: Investigation of Biodistribution and Speciation Changes of Orally Administered Dual Radiolabeled Complex, Bis(5-chloro-7-[131I]iodo-8-quinolinolato)[65Zn]zinc.
abstract: Many zinc (Zn) complexes have been developed as promising oral antidiabetic agents. In vitro assays using adipocytes have demonstrated that the coordination structures of Zn complexes affect the uptake of Zn into cells and have insulinomimetic activities, for which moderate stability of Zn complexes is vital. The complexation of Zn plays a major role improving its bioavailability. However, investigation of the speciation changes of Zn complexes after oral administration is lacking. A dual radiolabeling approach was applied in order to investigate the speciation of bis(5-chloro-7-iodo-8-quinolinolato)zinc complex [Zn(Cq)2], which exhibits the antidiabetic activity in diabetic mice. In the present study,65Zn- and131I-labeled [Zn(Cq)2] were synthesized, and their biodistribution were analyzed after an oral administration using both invasive conventional assays and noninvasive gamma-ray emission imaging (GREI), a novel nuclear medicine imaging modality that enables analysis of multiple radionuclides simultaneously. The GREI experiments visualized the behavior of65Zn and [131I]Cq from the stomach to large intestine and through the small intestine; most of the administered Zn was transported together with clioquinol (5-chloro-7-iodo-8-quinolinol) (Cq). Higher accumulation of65Zn for [Zn(Cq)2] than ZnCl2suggests that the Zn associated with Cq was highly absorbed by the intestinal tract. In particular, the molar ratio of administered iodine to Zn decreased during the distribution processes, indicating the dissociation of most [Zn(Cq)2] complexes. In conclusion, the present study successfully evaluated the speciation changes of orally administered [Zn(Cq)2] using the dual radiolabeling method.
authors.affiliation: Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama University.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Munekane
authors.forename: Masashi
authors.initials: M
authors.lastname: Ueda
authors.forename: Shinji
authors.initials: S
authors.lastname: Motomura
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Kamino
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Haba
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yoshikawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yasui
authors.forename: Shuichi
authors.initials: S
authors.lastname: Enomoto
mesh_terms: D000284:Administration, Oral; D000818:Animals; D002712:Chlorides / Q000008:administration & dosage* / Q000378:metabolism*; D007457:Iodine Radioisotopes / Q000008:administration & dosage* / Q000378:metabolism*; D008297:Male; D051379:Mice; D014018:Tissue Distribution / Q000187:drug effects / Q000502:physiology; D017967:Zinc Compounds / Q000008:administration & dosage* / Q000378:metabolism*
chemical_list: D002712:Chlorides; D007457:Iodine Radioisotopes; D017967:Zinc Compounds; C016837:zinc chloride