FATTY-ACID COMPOSITION OF LATE EMBRYONIC AND EARLY POSTNATAL RAT-BRAIN

The fatty acid (FA) composition and distribution in a variety of phosp holipids (PL) and neutral lipids (NL) at two discrete stages during th e embryonic rat brain development were investigated. Over 96% of the F A were acylated into fetal brain PL at embryonic day 17 after the peak of neuronal proliferation and at embryonic day 20, one day prior to d elivery. Phosphatidylcholine constituted approximately 60% of the tota l PL pool, phosphatidylethanolamine (PE) 30%, phosphatidylserine (PS) 6%, and phosphatidylinositol (PI) 4%. The diacylglycerols and triacylg lycerols constituted 1-2% of the fetal brain lipids. cr-linolenic acid (18:3n-3) and linoleic acid (18:2n-6) were found in very low amounts in all fetal brain PL and NL. The percentage of the n-6 polyunsaturate d FA, consisting of arachidonic acid (AA), 22:4n-6 and 22:5n-6, remain ed unchanged in all the fractions, except in PI, in which the proporti on of AA increased. The concentration of docosahexaenoic acid (DHA) in creased with age in all the fractions, with the bulk of accumulation a ccounted for by its increase in PE and, to a lesser extent, in PS. Thi s finding suggests a ''DHA accretion spurt'' during the last three day s of pregnancy.