Fatty acid composition of the rat pineal gland. Dietary modifications.

When compared to brain, the fatty acid composition of the rat pineal gland revealed that the total proportion of n-6 polyunsaturated fatty acids (PUFA) was 2.3-fold higher, whereas the proportion of n-3 fatty acids was similar. Specifically, 20:4(n-6) and 18:2(n-6) were respectively 1.56- and 11.80-fold higher in the pineal than in the brain, while the proportions of 22:6(n-3) were similar in both tissues. In addition, 18:1(n-9) was found 2.15-fold lower in the pineal. Feeding adult rats with fish oil concentrates induced a significant alteration of the polyunsaturated fatty acid composition of the pineal. There was a reciprocal replacement of the n-6 by the n-3 fatty acids. Conversely, in rats fed a n-3 fatty acid-deficient diet (sunflower oil or coconut oil diet), the pineal gland contained reduced proportions of n-3 fatty acids. We conclude that the pineal gland (i) differs from the brain in containing much higher proportions of 18:2(n-6) and from the other tissues for its high proportions of 22:6(n-3) and (ii) is highly sensitive to the n-3 fatty acid diet in contrast to what is known for the brain. These findings are discussed in the context of melatonin biosynthesis, the major hormone of the pineal gland.