Lack of effect of coumarin on unscheduled DNA synthesis in the in vivo rathepatocyte DNA repair assay

Citation
Aj. Edwards et al., Lack of effect of coumarin on unscheduled DNA synthesis in the in vivo rathepatocyte DNA repair assay, FOOD CHEM T, 38(5), 2000, pp. 403-409
Citations number
44
Categorie Soggetti
Food Science/Nutrition","Pharmacology & Toxicology
Journal title
FOOD AND CHEMICAL TOXICOLOGY
ISSN journal
02786915 → ACNP
Volume
38
Issue
5
Year of publication
2000
Pages
403 - 409
Database
ISI
SICI code
0278-6915(200005)38:5<403:LOEOCO>2.0.ZU;2-H
Abstract
The ability of coumarin to induce UDS in male Spague-Dawley CD rat hepatocy tes bt vivo was assessed using the unscheduled DNA synthesis (UDS) assay. F rom a preliminary toxicity study the oral maximum tolerated dose (MTD) of c oumarin was determined to be 320 mg/kg body weight. For the UDS studies, ra ts were treated with 0 (corn oil control), 32 tone-tenth the MTD), 107 tone -third the MTD) and 320 (MTD) mg/kg coumarin via oral gavage. Rats were als o treated with 20 mg/kg body weight dimethylnitrosamine (DMN) or 50 mg/kg b ody weight 2-acetylaminofluorene (2-AAF) as positive controls for the 2-4 h r and 12-16 hr expression of UDS, respectively. Hepatocytes were isolated b y Liver perfusion either 2-4 hr or 12-16 hr after treatment and cultured in medium containing [methyl-H-3]-thymidine for 4 hr and assessed for UDS by grain counting of autoradiographs. Coumarin treatment at doses of 32-320 mg /kg body weight had no statistically significant or dose-related effect on UDS in rat hepatocytes either 2-4 hr or 12-16 hr after dosing. In contrast, both DMN 2-4 hr after dosing and 2-AAF 12-16 hr after dosing produced sign ificant increases in UDS assessed as the net nuclear grain count. Both geno toxins also increased the percentage of hepatocyte nuclei with greater than 5 net grains. Treatment with coumarin, DMN and 2-AAF had no statistically significant effect on the proportion of rat hepatocytes undergoing replicat ive DNA synthesis. In summary, this study demonstrates that coumarin does n ot induce UDS in hepatocytes of male Sprague-Dawley CD rats after oral admi nistration at doses up to the MTD of 320 mg/kg. The responsiveness of the a nimals used in this study to genotoxic agents was demonstrated by the clear induction of DNA repair after treatment with DMN and 2-AAF. (C) 2000 Elsev ier Science. Ltd. All rights reserved.