title: In vivo bioassay to detect irinotecan-stabilized DNA/topoisomerase I complexes in rats.
abstract: Irinotecan is an anticancer agent that stabilizes topoisomerase I/DNA complexes. So far, no test system has been reported for directly determining irinotecan-induced stabilization of topoisomerase I/DNA complexes in organs in vivo. We adapted an 'in vivo complexes of enzyme to DNA' (ICE) bioassay to assess irinotecan activity in the stomach, duodenum, colon and liver of male Wistar rats after a single treatment with irinotecan (100 mg/kg body weight, intraperitoneally). This was compared to the control group receiving 0.9% sodium chloride intraperitoneally. In addition, the DNA strand breaking properties of irinotecan were measured in mucosal cells from the distal colon by single-cell gel electrophoresis (comet assay) to investigate the association of topoisomerase poisoning and DNA damage in vivo. A single dose of irinotecan significantly increased amounts of topoisomerase I covalently bound to DNA in stomach, duodenum, colon and liver. Concomitantly, the irinotecan-treated group showed significantly higher amounts of DNA strand breaks in colon mucosa cells compared to the control group. The ICE bioassay and the comet assay represent two test systems for investigating the impact of topoisomerase I poisons on DNA integrity in colon tissues of Wistar rats.
authors.affiliation: Department of nutrition Physiology and Biochemistry, Max Rubner-Institute, Karlsruhe, Germany.
authors.forename: Stephan W
authors.initials: SW
authors.lastname: Barth
authors.forename: Karlis
authors.initials: K
authors.lastname: Briviba
authors.forename: Bernhard
authors.initials: B
authors.lastname: Watzl
authors.forename: Nicole
authors.initials: N
authors.lastname: Jäger
authors.forename: Doris
authors.initials: D
authors.lastname: Marko
authors.forename: Melanie
authors.initials: M
authors.lastname: Esselen
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry* / Q000494:pharmacology; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D020552:Comet Assay; D004247:DNA / Q000378:metabolism; D053960:DNA Breaks; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D041981:Gastrointestinal Tract / Q000201:enzymology / Q000378:metabolism; D000077146:Irinotecan; D008099:Liver / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D046911:Macromolecular Substances / Q000378:metabolism; D008297:Male; D010865:Pilot Projects; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D059004:Topoisomerase I Inhibitors
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D046911:Macromolecular Substances; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D004247:DNA; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin