Effects of high corn oil diet on preneoplastic murine colons: prostanoid production and lipid composition.

In the present study, the effect of normal (5% by wt) and high (23.5% by wt) corn oil diets on prostanoid production and on the lipid composition of preneoplastic colonic epithelium was investigated. CF1 mice (female, 3-4-weeks-old) were fed a normal corn oil diet ad libitum and were treated with the colon carcinogen 1,2-dimethylhydrazine (DMH, 20 mg/kg/wk) or saline (control) for 24 wk. At this stage, all animals received the AIN-76 diet (normal corn oil) ad libitum. Following the last injection, half of the animals from each treatment group were randomly allocated to a high corn oil diet for 5 to 10 wk, whereas the remaining animals continued on the normal corn oil diet. After 5 wk of feeding, the colonic mucosa of carcinogen-treated animals had a higher level of bicyclic prostaglandin E2 (PGE2) than had the animals in the control groups; prostanoid synthesis in the colonic mucosa of control animals was unaffected by the high corn oil diet. Preneoplastic colonic mucosa of animals fed the high corn oil diet had a significantly higher level of PGE2 than corresponding control colonic mucosa. The 6-keto-prostaglandin F1 alpha/thromboxane B2 ratio was significantly lower in the DMH-treated groups than in the control groups, and was unaffected by dietary treatments. After 10 wk of feeding a particular diet, the differences in the fatty acid composition between the control and DMH-treated groups were minor. Our findings demonstrate that the preneoplastic colonic epithelium differs from that of normal epithelium with respect to prostanoid synthesis.