Dietary prevention of azoxymethane-induced colon carcinogenesis with rice-germ in F344 rats.
The modifying effect of dietary administration of defatted rice-germ and gamma-aminobutyric acid (GABA)-enriched defatted rice-germ on azoxymethane (AOM)-induced colon carcinogenesis was investigated in two experiments with male F344 rats. In the first experiment (the pilot study), the effects of the defatted rice-germ, the GABA-enriched defatted rice-germ and rice-germ on AOM-induced (15 mg/kg body wt once a week for 3 weeks) formation of aberrant crypt foci (ACF) were examined. The latter two preparations (2.5% in the diet) significantly inhibited ACF formation (P < 0.005). In the second experiment, a long-term study of the effects of rice-germ was done. One group was treated with AOM alone, four groups received the carcinogen and were fed the diets containing 2.5% rice-germ or 2.5% GABA-enriched defatted rice-germ for 5 (initiation phase) or 30 weeks (post-initiation phase), two groups were treated with rice-germ or GABA-enriched defatted rice-germ alone and one group was kept on the basal diet. At the termination of the study, dietary exposure to rice-germ during the initiation phase significantly reduced the incidence of colonic adenocarcinoma (71 versus 29%, P < 0.01). GABA-enriched defatted rice-germ or rice-germ during the post-initiation phase also decreased the frequency of colonic adenocarcinoma (71 versus 20%, GABA-enriched defatted rice-germ feeding, P < 0.01; 27%, rice-germ feeding, P < 0.01). These data suggest that constituents of rice-germ are possible dietary preventatives for human colon cancers.
Kawabata
K
K
First Department of Pathology, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu 500-8705, Japan.
Tanaka
T
T
Murakami
T
T
Okada
T
T
Murai
H
H
Yamamoto
T
T
Hara
A
A
Shimizu
M
M
Yamada
Y
Y
Matsunaga
K
K
Kuno
T
T
Yoshimi
N
N
Sugie
S
S
Mori
H
H
D000818:Animals; D001397:Azoxymethane; D002273:Carcinogens; D003110:Colonic Neoplasms / Q000139:chemically induced* / Q000276:immunology / Q000517:prevention & control*; D008297:Male; D012275:Oryza; D010865:Pilot Projects; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344
D002273:Carcinogens; D018809:Proliferating Cell Nuclear Antigen; D001397:Azoxymethane