EFFECT OF DIETARY OILS CONTAINING GRADED AMOUNTS OF 18/3 N-6 AND 18/4 N-3 ON CELL PLASMA-MEMBRANES

Rats were fed diets containing a constant supply of lipids (10% by weight) differing from one another in the content of oleic acid (18:1 n-9), linoleic acid (18:2 n-6), and most peculiar 18-carbon polyunsaturated fatty acids, such as gamma-linolenic (18:3 n-6), alpha-linolenic (18:3 n-3), and stearidonic acid (18:4 n-3). Heart plasma membrane fatty acid composition from rats fed the different diets was affected. The diet containing the highest oleic acid content (olive oil diet) and the lowest PUFA content produced a significant decrease of linoleic acid content, while the oleic acid content was significantly lower when diets contained the lowest oleic acid percentage (black currant oil diet). Similarly, liver plasma membrane fatty acid composition was influenced by the different diets; in particular a significant higher content of the 20:4 n-6 was observed when rats were fed diets containing black currant oil (alone or into a 1:1 mixture with alive oil). Finally, the three diets tested influence only to a low level of significancy the fatty acid composition of the brain plasma membrane: Accordingly, the specific activity of 5'-nucleotidase, a typical cell plasma membrane enzyme, was not affected by diets neither in brain, nor in heart membrane preparations. On the contrary, the 5'-nucleotidase activity was highest in the membrane of liver cells from rats fed olive ail. A correlation between 5'-nucleotidase activity and membrane fatty acid composition cannot be stated in the conditions examined, however, possible biochemical mechanisms as the basis of 5'-nucleotidase behavior are discussed.