EFFECTS OF DIETARY OILS ON FATTY-ACID COMPOSITION AND LIPID-PEROXIDATION OF BRAIN MEMBRANES (MYELIN AND SYNAPTOSOMES) IN RATS

The effects of dietary oils on the fatty acid composition and lipid pe roxidation of myelin and synaptosomes isolated from rat brain were stu died. The animals were fed diets rich (15% wt/wt) in either long chain n-3 fatty acids (fish oil), n-6 fatty acids (soybean oil), or saturat ed fatty acids (coconut oil) for 6 weeks. Fish oil led to a significan t increase in the n-3 fatty acid percentage in both membranes with a c oncomitant decrease in n-6 fatty acids percentage in myelin but not in synaptosomes. Soybean and coconut oils influenced less strictly the b rain membranes' fatty acid composition. A higher peroxidation rate and a lower concentration of vitamin E was observed in brain membranes of the fish oil group compared with the coconut group, with intermediate values in the soybean oil group. However, no differences among the ex perimental animals were observed in thiobarbituric acid reacting subst ances (TBARS) of brain membranes, although in serum TBARS concentratio ns increased in proportion to dietary PUFA content, suggesting that th e brain is more protected in vivo by oxidative challenge. The data als o indicate that dietary oils may differently affect the fatty acid com position of isolated brain membranes, with synaptosomes being more sus ceptible to oxidative stress than myelin membranes.