Increasing dietary linoleic acid in young rats increases and then decreases docosahexaenoic acid in retina but not in brain.

The accumulation of fatty acids in retina, brain, liver, and plasma of 30-day-old rat pups consuming various levels of linoleic acid (LA, 18:2n-6) and constant alpha-linolenic acid (ALA, 18:3n-3) is reported. Dams were fed graded levels of LA during gestation and lactation, and the pups were maintained on the diet of their dams until the end of the brain growth spurt at 30 d of life. Milk, and pup brain, retina, liver, and plasma were analyzed quantitatively for fatty acid profile. The percentage of docosahexaenoic acid (DHA, 22:6n-3) in retina increased from an LA-deficient dietary level, peaked at the 9:1 (LA/ALA) level, then fell for the 41:1 and 69:1 levels. In contrast, the brain DHA percentage was unaffected by dietary LA levels. Retinal unsaturated fatty acid levels paralleled liver and plasma levels. The milk fatty acid composition mirrored the diets. These data show that the retinal fatty acid composition responds sensitively to dietary fatty acid composition, similar to liver and plasma, while the brain unsaturate composition is nearly independent of dietary composition.