Gastro-intestinal tumors in mice of three strains maintained on fat-enriched diets

Mice of three strains were used in the present experiments. The control mice (group 1, 7 and 9) have been kept on Purina chow only. For the experimental mice of the T.M. strain the Purina chow was supplemented with refined corn oil (group 2), crude corn oil (group 3), regined corn oil plus free fatty acids (group 4), Monoolein (group 5) and Monostearin (group 6). For the experimental mice of the BALB/c and C57 Br. strains (group 8 and 10) Purina chow was supplemented with raw egg yolk. Very few of the control mice developed tumors of the forestomach (3/195 mice in group 1 and 1/165 mice in group 9) and none of them developed pyloric or intestinal tumors. Among the mice maintained on the fat-enriched diets the incidence of tumors of the forestomach and of the pyloric glandular part of the viscus was relatively high, except for the mice in group 6, maintained on Purina chow supplemented with monostearin. Intestinal tumors were found only in mice of the BALB/c and C57 Br. strains maintained on Purina chow supplemented with egg yolk. The tumors were for the most part polyps, except for adenocarcinomas developed by three C57 Br. mice from group 10. The difference between mice of the T.M. strain, (which did not develop intestinal tumors), and those of the BALB/c and C57 Br. strains, (which developed intestinal tumors), may be due to a difference in their susceptibility or to the difference in their diets.