DIETARY OXIDIZED LINOLEIC-ACID MODIFIES LIPID-COMPOSITION OF RAT-LIVER MICROSOMES AND INCREASES THEIR FLUIDITY

The effect of dietary oxidized oil on the lipid composition, fluidity and function of rat liver microsomes was studied, Male growing rats we re fed diets containing 10 g/100 g of a fresh (control) or oxidized (e xperimental) linoleic acid-rich preparation for 4 wk, High levels of f luorescent compounds and of thiobarbituric acid reactive substances in dicated the occurrence of substantial lipid peroxidation in the micros omes of the experimental rats. The fluidity of the liver microsomes de rived from rats fed the experimental diet was significantly higher tha n that of the membranes of the controls. This was due to profound diff erences in lipid composition of the liver microsomes, namely, a lower cholesterol to phospholipid molar ratio and a greater arachidonic acid content in the phospholipids of the rats fed the experimental diet. T he fluidity differences were accompanied by greater activity of the mi crosomal enzymes, aldehyde dehydrogenase and NADPH cytocrome C reducta se. The study demonstrated that ingestion of oxidized lipids caused pr ofound alterations in membrane composition, fluidity and function. The se alterations are likely to be associated with an enhanced cholestero l turnover, as indicated by the greater cholesterol excretion observed for the experimental rats.