EFFECT OF DIETARY VITAMIN-A ON FORESTOMACH TUMORIGENESIS DURING THE TOTAL AND POSTINITIATION STAGES IN MICE TREATED WITH HIGH-DOSE OR LOW-DOSE BENZO(A)PYRENE

The effects of dietary vitamin A on forestomach tumorigenesis during t he total stage of the initiation and postinitiation periods and during the postinitiation stage were evaluated in ICR/Jcl mice treated with either high or low doses of benzo(a)pyrene (B(a)P). In experiment 1, t he animals were initiated with a high carcinogenic dose of B(a)P to a total of 20 mg, while in experiment 2 the animals were treated with a Low dose of B(a)P to a total of 2 mg. A control group of animals recei ved no carcinogens. Five different dietary levels of vitamin A supplem ents were used in each experiment and in the control study. In experim ent 1, a high incidence of tumorigenesis was observed in every group, with 74% to 96% developing papilloma and 19% to 46% developing carcino ma. In experiment 2, the incidence of tumorigenesis in the high-dose v itamin A groups, including those given during the total and postinitia tion stages, was found to be significantly reduced at 7.4%, compared w ith that in the low-dose vitamin A group of 57.7% (P < 0.05). These re sults suggest that a high dietary level of vitamin A can reduce the in cidence of tumorigenesis when low carcinogenic dose levels of B(a)P ar e given in both the total and postinitiation stages.