Observations on lipid composition with particular reference to cardiolipin of rat heart after feeding rapeseed oil.

The influence of dietary rapeseed oil on the lipid classes and fatty acid pattern of rat heart homogenate and mitochondria has been investigated after feeding a diet with 9.8 weight- % erucic acid for 10 days and 1.4 and 2.6% erucic acid for 28 days. The rats treated with 9.8% erucic acid showed a significant increase in the triglycerides of the heart mitochondria. This tendency was much less pronounced in rats treated with 1.4 resp. 2.6% erucic acid. These results confirm those of other investigators. A slight increase in the cholesterol esters of the mitochondria could be seen in all the treated rats. The total phospholipids were decreased in the experiment with 9.8% erucic acid and slightly increased in experiments with 1.4 and 2.6% erucic acid. The concentration of phosphatidylcholine showed a tendency to increase and the concentration of phosphatidylethanolamine to decrease in the experiment with 9.8% erucic acid in the diet. The concentration of cardiolipin was mainly unchanged. In all experiments the triglycerides of the heart mitochondria showed a high content of erucic acid. The fatty acids of the cholesterol esters of the heart mitochondria were also influenced of dietary rapeseed oil but to a less extent than the triglycerides. The fatty acids of phosphatidylcholine, phosphatidylethanolamine and cardiolipin were all influenced by the dietary rapeseed oil, but the erucic acid seemed to have a specific affinity to cardiolipin. Cardiolipin of rat heart mitochondria was isolated and identified with gas chromatography and mass spectrometry. The isolated cardiolipin was found to contain 12 per cent erucic acid after feeding 9.8% erucic acid as rapeseed oil for 10 days. Similar results were obtained after feeding glyceryl trierucate for 5 days to rats. The incorporation of erucic acid into cardiolipin was followed by a corresponding decrease of linoleic acid. This observation is of great interest because the molecular structure of fatty acids in lipid molecules has a profound influence of the packing of these molecules in a bilayer. Since cardiolipin is a component of the inner membrane of mitochondria its high affinity for erucic acid might influence the normal function of the inner membrane of heart mitochondria.