MODIFYING EFFECT OF DIETARY-FAT ON BENZO[A]PYRENE-INDUCED RESPIRATORY-TRACT TUMORS IN HAMSTERS

Groups of 40 Syrian golden hamsters of both sexes were fed diets containing either 5% fat (control), 20% saturated fat (beef tallow) or 20% unsaturated fat (sunflower seed oil) from weaning and during the whole experimental period (up to 656 days). Respiratory tract tumors were induced by intratracheal instillation of benzo[a]pyrene attached to ferric oxide and suspended in saline. Mortality was slightly but not statistically significantly higher in the high fat groups than in the low fat control group. Microscopic examination of the respiratory tract revealed an increased number of tumor-bearing animals, an increased multiplicity of respiratory tract tumors and an increased total number of respiratory tract tumors in animals fed high fat diets. The tumor-enhancing effect of fat was most pronounced in the high unsaturated fat group. In particular, epidermoid papillomas, epidermoid carcinomas and combined epidermoid and adenocarcinomas contributed to the observed differences in tumor response among groups. Dietary fat apparently enhances benzo[a]pyrene-induced respiratory tract carcinogenesis in hamsters.