Rahman KM, Sugie S, Okamoto K, Watanabe T, Tanaka T, Mori H. Modulating effects of diets high in omega-3 and omega-6 fatty acids in initiation and postinitiation stages of diethylnitrosamine-induced hepatocarcinogenesis in rats.
Jpn J Cancer Res 1999;
90:31-9. [PMID:
10076562 PMCID:
PMC5925980 DOI:
10.1111/j.1349-7006.1999.tb00662.x]
[Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The effects of sardine fish oil or corn oil on diethylnitrosamine (DEN)-induced hepatocarcinogenesis were investigated in male F344 rats. Starting at 5 weeks of age, animals were divided into 11 groups and fed 23.5% corn oil (HCO) (groups 1 and 7) or 5% corn oil (LCO) (groups 2 and 8), 22.5% sardine oil + 1% corn oil (FO) semipurified diet (groups 3 and 9) or basal diet (CE-2) (groups 4-6, 10 and 11). At 6 weeks of age, all animals except the vehicle-treated groups were given DEN (200 mg/kg body weight, i.p. once weekly for 3 weeks). One week after the final exposure to DEN, groups 1-3 were changed to the basal diet, and groups 4-6 were switched to the HCO, LCO or FO diet, respectively. Animals in groups 1-3 and 10 were given drinking water containing 0.05% phenobarbital (PB). Liver sections from the animals at the termination of the experiment (24 weeks) were doubly stained for glutathione S-transferase placental form (GST-P) and silver-stained nucleolar organizer regions (AgNORs). The multiplicity of hepatocellular neoplasms of group 1 was significantly larger than that of group 2 or 3. The number of GST-P-positive foci of group 2 or 3 was significantly smaller than that of group 1. Among the groups fed the experimental diets in the postinitiation phase (groups 4-6), no significant difference was found in the incidence of liver tumors. AgNORs values of the enzyme-altered foci in rats of the HCO diet groups were larger than those of the other diet groups. These results indicate that the enhancing effect of a high dose of corn oil in hepatocarcinogenesis is mainly present during the initiation phase but not during postinitiation phase, and fish oil rich in polyunsaturated omega-3 fatty acids could inhibit DEN-induced hepatocarcinogenesis in rats.
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