Enhancement of tumor formation in mouse lung by dietary butylated hydroxytoluene

Male A/J mice were injected i.p. with a single dose of urethan and fed 0.75% butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) or ethoxyquin in the diet. All animals were killed 4 months after urethan and the number of lung tumors counted. Exposure to BHT, but not to BHA or ethoxyquin significantly enhanced formation of lung tumors if animals were given the BHT-containing diet once a week for 8 consecutive weeks or were kept on it continuously for 8 weeks. Prefeeding mice with BHT had no effect on tumor formation but prefeeding BHA reduced the number of tumors formed by urethan. It is concluded from this and previous work that in mouse lung BHT enhances tumor formation regardless of route of administration and over a 100-fold dose range.