[Chemoprevention of 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine-induced carcinogen-DNA adducts by Chinese cabbage in rats].
OBJECTIVE
To examine the preventive effect of Chinese cabbage (Brassica chinensis) against colon carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced PhIP-DNA adduct formation in rats and its possible mechanism.


METHODS
Sprague-Dawley rats were maintained for 10 days on lab chow or chow containing 20% (w/w) freeze-dried cabbage powder prior to administration of a single dose of PhIP (10 mg/kg) by oral gavage. Rats were sacrificed at 20 h after PhIP treatment and PhIP-DNA adducts in the colon, heart, lung, and liver were analyzed using 32P-postlabeling technique. Levels of hepatic cytochrome P450 (CYP) 1A1 and 1A2, as indicated by 7-ethoxyresorufin O-deethylase and 7-methoxyresorufin O-demethylase activity, and cytosolic glutathione S-transferases (GST) towards CDNB in the liver, lung and colon mucosa were measured.


RESULTS
Rats pre-treated with Chinese cabbage and given a single dose of PhIP had reduced levels of PhIP-DNA adducts in the colon, heart, lung and liver, with an inhibition rate of 82.3, 60.6, 48.4 and 48.9%, respectively (P < 0.01). Enzyme assays revealed that both CYP1A1 and 1A2 were induced by cabbage, but the induction was preferential for CYP1A1 over 1A2 (80.6% vs 50.2%). GST activity towards CDNB in the liver and lung, but not colon, was also significantly induced by the cabbage.


CONCLUSIONS
The results indicate a preventive effect of Chinese cabbage against PhIP-initiated carcinogenesis in rats and the mechanism is likely to involve induction of detoxification enzymes.
Cancer Institute(Hospital), Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing.
W
W
Tan
D
D
Lin
Y
Y
Xiao
D000818:Animals; D001937:Brassica; D002273:Carcinogens / Q000493:pharmacokinetics*; D003106:Colon / Q000378:metabolism*; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D018736:DNA Adducts / Q000096:biosynthesis*; D005982:Glutathione Transferase / Q000378:metabolism; D007093:Imidazoles / Q000493:pharmacokinetics*; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D002273:Carcinogens; D018736:DNA Adducts; D007093:Imidazoles; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D019363:Cytochrome P-450 CYP1A1; D005982:Glutathione Transferase