THE EFFECT OF DIETARY LIPIDS ON RAT-LIVER MITOCHONDRIAL SWELLING

The swelling of liver mitochondria resulting from changes in the dieta ry fatty acid (FA) was investigated in rats fed two lipid diets far tw o or four months. Female Sprague-Dawley Fats Were fed two semi-synthet ic and isocaloric diets. One diet (CO diet) contained 10% coconut fat (rich in saturated fatty acids, SFA) while the other (SO diet) contain ed 10% sunflower seed oil (rich in unsaturated fatty acids, UFA). The initial velocity (Vo) was used to determine the velocity of the sponta neous and phosphate- or calcium-induced swelling of rat liver mitochon dria. The changes in the fatty acid composition of the mitochondrial m embranes were expressed as the unsaturation index, as well as the tota l content of saturated and unsaturated fatty acids and their ratios. T he liver mitochondrial phospholipid fatty acid composition was very si milar in both diet groups, in spite of the differences in dietary lipi d fatty acid content. Only the 16:0, 16:1 (omega-7) and 16:1 (omega-9) fatty acids of the liver mitochondrial phospholipids differed signifi cantly during the experiment. In general, the diets and the length of treatment had no significant influence on the extent of swelling. Howe ver, for animals fed the SO diet, significant differences in the for V o of the phosphate- and calcium-induced swelling was observed. This re sult probably reflects greater fluidity of the mitochondrial membrane due to the high content of the fatty acid residues which would produce a more flexible and less stable membrane system.