Effects of different levels of dietary fat on methyl-nitrosourea-induced mammary carcinogenesis in correlation with parameters of fat metabolism in female Sprague-Dawley rats.

The aim of this study was to elucidate the effects of different levels of dietary fat on methyl-nitrosourea-induced rat mammary carcinogenesis in correlation with parameters of the fat metabolism. 90 female Sprague-Dawley rats were initiated i.v. with 25 mg MNU/kg on day 50 of life. For a period of 6 months, beginning after the day of initiation, the animals received either a control diet (12% of total energy as fat, Group I) or one of the fat-enriched semisynthetic diets (25 en% of fat, Group II, or 45 en%, Group III, respectively) at an isocaloric level of 50 kcal/rat/day. The principal observations of this experiment were: (1) The fat content of diet did not significantly influence mammary carcinogenesis. (2) The values of plasma total lipids, cholesterol and triglycerides and their density separated VLDL and LDL-fractions showed a significant time-dependent increase. (3) HDL-values of cholesterol and triglycerides showed no changes in dependence to time and fat content of the diet. (4) The liver lipid concentrations of groups increased significantly with dietary fat content.