Effect of acetyl-coa of fatty acid synthesis in selected cell fractions of normal mouse mammary tissue an adenocarcinomas
It has been suggested that membrane characteristics associated with carcinomas could be related to an altered molecular structure of lipids in the plasma membrane. The microsomal fraction, mitochondria and soluble fractions of the cell are major sites of de novo synthesis and elongation of fatty acids. It was the purpose of this study to compare the utilization of AcSCoA in the biosynthetic pathway for saturated fatty acids in tumor and normal tissue, and discern if any deviations in the initial steps of the pathway were responsible forr the observed differences in the plasma membrane of tumors. Labeled 14C-AcSCoA was incorporated into saturated fatty acids in both adenocarcinomas and normal mammary tissue. The distribution and degree of incorporation of labeled 14C-AcSCoA was hoped to demonstrate any deviations in the pathway.Crude supernate, microsomal fraction, mitochondria and soluble fractions were isolated from mammary adenocarcinomas and from normal mammary tissue of Strain A female mice by differential centrifugation. The activity of fatty acid synthetase in the soluble fraction was determined. The crude supernate, the soluble fraction, the mitochondria + soluble fraction and the microsomal fraction + soluble fraction of both the adenocarcinoma and normal mammary tissue were incubated with labeled 14C-AcSCoA, Ma1SCoA and all necessary cofactors. The now labeled fatty acids were extracted from these incubation mixtures. The total percent of incorporated labeled 14C-AcSCoA in each fraction was determined. The percent of incorporation of label into individual saturated fatty acids in each fraction was determined by gas liquid chromatography and liquid scintillation counting. Carrier mixtures of known fatty acids were added to the samples used for GLC analysis to confirm the identity of the labeled fatty acids.Results of this study show that the percent of labeled i4C-AcSCoA incorporated into the various saturated fatty acids was similar in tumor and normal tissue. However, the total uptake of AcSCoA was nearly twice as great in normal tissue. The activity of fatty acid synthetase appearsto be characteristic of each individual mouse. In tumored mice fatty acid synthetase activity appears to be related to tumor weight, that is the larger the tumor the greater the activity. These results do not demonstrate support for a shift in the biosynthesis of saturated fatty acids in carcinomas. It may be that the altered lipid composition of the plasma membrane of tumor cells arises from the carcinoma's ability to utilize exogenous fatty acids.