Dietary linoleate enhances the development of mammary tumors while dietary stearate has a retarding effect. Since linoleate is a precursor of prostaglandin E2 and elevated levels of prostaglandin E2 have been shown to be associated with tumor development, levels of dietary linoleate directly influence the levels of prostaglandin E2 available for tumor development. The development of new tumor tissue also involves a high demand for fatty acids to be incorporated into cell membranes and this demand is for specific types of fatty acids to maintain the required membrane fluidity.Several enzymes play key roles in the synthesis and desaturation of the fatty acids which are converted to prostaglandins and are synthesized for membrane incorporation. Among these are fatty acid synthetase and linoloeyl coenzyme A desaturase. This study examined the activity of these two enzymes in liver tissue of mice maintained on test diets containing varying proportions of the fatty acids stearate and linoleate.Animals fed a high fat (15% of total) diet containing 13.1% stearate were found to have higher linoloeyl coenzyme A deeaturaae activity than animals fed a low fat diet or a high fat diet containing 11.3% linoleate diets. Animals fed the high fat, high stearate diet were found to have a higher fatty acid synthetase activity than animals fed either a low fat diet or the high fat, high linoleate diet.

Changes in the plasma membrane phospholipid composition may alter the structure and/or fluidity and lead to a variety of changes in membrane functions. Dietary fats are known to influence the composition of lipids in the plasma membrane. The purpose of this investigation was to compare effects of dietary linoleic and stearic acid on the composition of the phospholipids in the plasma membranes of mammary tumors in A/St mice.Plasma membranes were isolated and lipids were extracted. Phospholipids were separated by thin-layer chromatography and identified by detection with molybdenum blue reagent. The Rf values and integration of optical densities were used to compare phospholipid composition in membranes of tumors from mice fed experimental diets. It appears that the amount of dietary fat, but not the type, affects the phospholipid distributions. The phosphatidylinositol was the phospholipid most affected, representing the smallest amount in membranes from tumors in mice fed the low fat diets. / Department of Biology

It has been suggested that plasma membranes play a role in tumor production. Changes in plasma membrane lipid composition may change membrane fluidity and disrupt cellular communication. These changes in membrane lipid composition appear to be related to the fatty acid content of the animal's diet. The purpose of this investigation was to compare the effect of dietary linoleic and stearic acids and tumor size on cholesterol/phospholipid ratios and fatty acids in membranes of mammary adenocarcinomas.Plasma membranes of mammary tumors from Strain A/St mice were isolated by centrifugation and the lipids extracted. Phospholipid content was assayed by the method of Bartlett (102); cholesterol and fatty acids by gas liquid chromatography.Plasma membranes of tumors from mice fed the high linoleic diet (SAFF) were found to have the highest cholesterol/phospholipid ratios (Mean=0.396); mice fed high stearic acid diets produced tumors with the lowest ratios (0.280). Membranes of tumors from mice fed SA-4 and Stock diets had intermediate ratios (0.0.341 and 0.0.346, respectively). / Department of Biology