摘要Aristolochic acid I (AAI) is a well-known nephrotoxic carcinogen,which is currently reported to be also associated with hepatocellular carcinoma (HCC).Whether AAI is a direct hepatocarcinogen remains controversial.In this study we investigated the association between AAI exposure and HCC in adult rats using a sensitive rat liver bioassay with several cofactors.Formation of glutathione S-transferase placental form-positive (GST-P+) foci was used as the marker for preneoplastic lesions/clonal expansion.We first conducted a medium-term (8 weeks) study to investigate whether AAI had any tumor-initiating or-promoting activity.Then a long-term (52 weeks) study was conducted to determine whether AAI can directly induce HCC.We showed that oral administration of single dose of AAI (20,50,or 100 mg/kg) in combination with partial hepatectomy (PH) to stimulate liver proliferation did not induce typical GST-P+ foci in liver.In the 8-week study,only high dose of AAI (10 mg· kg-1· d-1,5 days a week for 6 weeks) in combination with PH significantly increased the number and area of GST-P+ foci initiated by diethylnitrosamine(DEN) in liver.Similarly,only high dose of AAI (10 mg· kg-1· d-1,5 days a week for 52 weeks) in combination with PH significantly increased the number and area of hepatic GST-P+ foci in the 52-week study.No any nodules or HCC were observed in liver of any AAI-treated groups.In contrast,long-term administration of AAI (0.1,1,10 mg· kg-1· d-1) time-and dose-dependently caused death due to the occurrence of cancers in the forestomach,intestine,and/or kidney.Besides,AAI-DNA adducts accumulated in the forestomach,kidney,and liver in a time-and dose-dependent manner.Taken together,AAI promotes clonal expansion only in the high-dose group but did not induce any nodules or HCC in liver of adult rats till their deaths caused by cancers developed in the forestomach,intestine,and/or kidney.Findings from our animal studies will pave the way for further large-scale epidemiological investigation of the associations between AA and HCC.