THE EFFECT OF DIFFERENT DIETARY FATS ON THE LIPID COMPOSITION OF SWINE CARDIAC PLASMA MEMBRANE

The purpose of the experiment was to see if diets containing different fats would change the lipid composition of swine cardiac sarcolemma. Eighteen adult finishing swine were fed three different diets for two months; the diets contained either 1% corn oil (basal diet), 10% corn oil (corn oil diet), or 1% corn oil plus 9% hydrogenated soybean oil (trans fat diet). After slaughter, the hearts were taken and the sarcolemma isolated. The sarcolemma was identified by an increase in Na('+),K('+)-ATPase and decrease in succinic dehydrogenase and Ca('++),K('+)-ATPase activities. Electron and phase contrast microscopy showed that the isolate was relatively free of contractile proteins and contaminating structures. The yield of isolate protein to that of the initial homogenate was approximately 7% per preparation. Lipids were extracted from the isolate and analyzed for phospholipid and cholesterol content. Blood samples were also taken for cholesterol analysis. No significant differences in plasma cholesterol values were found among dietary groups; higher percent fat groups, however, had larger values than the basal group. Also, no significant difference among groups was determined for tissue cholesterol content. No significant differences among groups were found for the cholesterol/phospholipid molar ratio. The phospholipid structure of the cardiac sarcolemma was found to primarily contain phosphatidyl choline and phosphatidyl ethanolamine. The phospholipid composition was similar for the basal and trans fat groups, but the corn oil group showed a significant decrease in phosphatidyl ethanolamine and an increase in phosphatidyl serine. The major phospholipid classes were analyzed for their individual fatty acid content. Trans-octadecenoic acid was incorporated into the phospholipid structure of cardiac sarcolemma from the trans fat dietary group only. Approximately 3% trans-18:1 was found in the phosphatidyl choline fraction and (TURN)8.3% in the phosphatidyl ethanolamine fraction. A decrease in stearic acid in the trans group was probably due to competition with the trans-18:1 fatty acid. The corn oil group incorporated more 18:2 than the other groups. The ratio of saturates (including trans-18:1) to unsaturates remained the same across dietary groups for each major phospholipid fraction.