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Protective Action of Stock Diets against the Cancer-Inducing Action of 2-Acetylaminofluorene in Rats^*

( Department of Animal Husbandry and Nutrition, Agricultural Experiment Station of the Alabama Polytechnic Institute, Auburn, Ala.)

When weanling rats of either the AES or the Sprague-Dawley strain were fed semi-purified diets containing 0.03 per cent of 2-acetylaminofluorene, they survived about 27 weeks, developed mammary tumors in over 90 per cent of cases in 13 to 22 weeks, and developed ear duct and liver tumors in 50–60 per cent of cases. Rats of the Sprague-Dawley strain appeared to be particularly susceptible to mammary tumor induction.

Rats fed the same level of the carcinogen on a diet of natural foodstuffs (stock diets) were still free of visible tumors up to the 28th week, on the average. Eventually, mammary tumors developed in 8 of 24 animals on such diets (33 per cent incidence). Survival on such diets was extended to 42 weeks, with 10 of 12 rats developing ear duct tumors and 7 of 12 rats developing liver tumors before death occurred. One of the 12 rats remained tumor-free throughout the experiment.

Modified stock diets produced results intermediate between those obtained on semi-purified and stock diets.

The results emphasize that semi-purified or purified diets are preferable to diets of natural foodstuffs for the early and consistent production of mammary and other type tumors in young female rats.

^* Published with the approval of the Director, Alabama Agricultural Experiment Station. This work was supported in part by a grant from the Nutrition Foundation, Inc., New York, N.Y.

Received 11/17/51.