Effect of maternal dietary arachidonic or linoleic acid on rat pup fatty acid profiles

Rapidly growing neonatal mammals accrete relatively large quantities of long chain (≥C20) polyunsaturated fatty acids (LCP) in membrane phospholipids. We have examined accumulation of ω6 LCP in suckling neonatal rat pups during the first 14 d of life when their dams received essential fatty acids in the form of triglycerides containing linoleic acid or arachidonic acid. Dietary levels of these fatty acids were either 1 or 5% of total dietary fatty acids. The fatty acid profile of pup stomach contents (composed solely of the dams' milk) and plasma lipids, as well as liver and brain phospholipids, were determined. Stomach linoleic and arachidonic acid levels reflected the diet of the dams. Pup plasma and liver arachidonic acid levels increased progressively from the group receiving 1% linoleic acid to 5% linoleic acid and from 1% arachidonic acid to 5% arachidonic acid. Interestingly, brain phosphatidylethanolamine and phosphatidylcholine arachidonic acid levels were more stable than plasma or liver levels. These results suggest that the brain may be capable of either selective transport of ω6 LCP or chain elongation/desaturation of linoleic acid. These data indicate that care must be exercised when adding LCP to infant formula since widely divergent accretion rates of arachidonic acid may occur in various tissues.