Preferential incorporation of sn-2 lysoPC DHA over unesterified DHA in the young rat brain.

The uptake and metabolism of [3H]docosahexaenoic acid (DHA) esterified at the sn-2 position of lysophosphatidylcholine (lysoPC DHA) and in the unesterified form, both bound to albumin, was studied in 20-day-old rats. LysoPC DHA was preferentially recovered in the brain (4-5% of the injected radioactivity) over the unesterified form of DHA (0.3-0.4%). Conversely, the lysoPC form was taken up less than or at the same extent as the unesterified form by the liver, heart, and kidney. In the brain, DHA was mainly recovered in phosphatidylethanolamine whether the esterified or the unesterified form was used, although DHA from lysoPC was esterified at the same extent in phosphatidylcholine and phosphatidylethanolamine after 2.5 min. The uptake of labeled palmitic, oleic, linoleic, and arachidonic acids, esterified or not in lysophosphatidylcholine, was also studied in brain, liver, heart, and kidney. Only the brain preferentially incorporated unsaturated (but not saturated) lysoPC, with the uptake increasing with the degree of unsaturation of the fatty acid moiety. These results strongly suggest that the young rat brain specifically utilizes albumin-lysoPC-containing polyunsaturated fatty acids.