Enhancement of pancreatic carcinogenesis by a dietary unsaturated fat in rats treated with saline or N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine.

The effect of diets high in an unsaturated fat on the enhancement of pancreatic carcinogenesis in saline-treated rats and in rats treated with N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) was examined. Young male LEW rats were treated with a single dose of HPOP (160 mg/kg body wt) or saline, fed diets containing 5 or 20% corn oil, and then autopsied 12 months later. The pancreata of HPOP-treated rats fed the diet with 5% fat contained multiple foci and nodules of atypical acinar cells (AACN), acinar cell adenomas, and localized carcinomas. Rats fed the diet with 20% fat developed a similar spectrum of pancreatic lesions and also developed carcinomas that showed local invasion or metastasis to regional lymph nodes. The incidence and multiplicity of localized carcinomas was significantly higher in the group that was fed the high-fat diet. HPOP also induced neoplasms in the liver, lungs, and kidneys, but none of these had a higher incidence in the group fed the high-fat diet. Among rats that received no carcinogen, the incidence of AACN was high, but the multiplicity of these lesions was low, an average of three per pancreas in groups fed both levels of fat; however, the average area of AACN transections was larger in the high-fat diet group. One acinar cell adenoma and 1 carcinoma developed in the group of 11 rats fed the 20% corn oil diet, whereas no neoplasms developed in the group of 12 rats fed the 5% corn oil diet. Although the incidence of pancreatic neoplasms is not significantly different in these 2 groups, the data are consistent with the hypothesis that initiated foci are promoted to grow and become neoplasms in the pancreas of rats that are fed diets with a high content of unsaturated fat--as was demonstrated in the HPOP-treated rats.