Absence of an inhibitory effect of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis in rats fed low- or high-fat diets.
The potential inhibitory effects of a vegetables-fruit mixture on the initiation and promotion phases of azoxymethane-induced colorectal carcinogenesis were examined in rats fed low- or high-fat diets. Rats were fed low-fat diets (20 energy percent, Diets A and B) or high-fat diets (40 energy percent, Diets C and D), supplemented with a vegetables-fruit mixture (19.5% wt/wt, Diets B and D) or unsupplemented (Diets A and C) for 36 weeks. After the animals were maintained on the respective diets for four weeks, they were given three weekly injections of azoxymethane at 15 mg/kg body wt sc. Eight weeks after the start of the study, animals maintained on Diet A were switched to Diet B or C or maintained on the same diet. Animals maintained on Diet B or D were switched to Diet A or C, respectively. Furthermore, animals maintained on Diet C were switched to Diet A or D or maintained on the same diet. Multiplicity of colorectal tumors did not differ between groups fed a vegetables-fruit mixture during the initiation or the promotion phase (Group B-->A vs. Group A-->B; Group D-->C vs. Group C-->D). However, multiplicity was significantly lower in animals fed low-fat diets than in animals fed high-fat diets in combination with a vegetables-fruit mixture (Group A-->B/B--A vs. Group C-->D/D-->C). Furthermore, multiplicity was significantly increased in groups fed a high-fat diet during the promotion phase only in comparison with animals fed a low-fat diet during the whole experiment (Group A-->C vs. Group A-->A). No other differences in multiplicity or tumor incidences were observed among the eight experimental groups.
Rijnkels
J M
JM
Department of Toxicology, Wageningen Agricultural University, The Netherlands. office@algemeen.tox
Hollanders
V M
VM
Woutersen
R A
RA
Koeman
J H
JH
Alink
G M
GM
D000230:Adenocarcinoma / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control; D000236:Adenoma / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control; D000818:Animals; D001397:Azoxymethane; D002273:Carcinogens; D015179:Colorectal Neoplasms / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D004032:Diet; D018752:Diet, Fat-Restricted; D004041:Dietary Fats / Q000008:administration & dosage*; D005638:Fruit; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D014675:Vegetables
D002273:Carcinogens; D004041:Dietary Fats; D001397:Azoxymethane