Fatty acid composition of late embryonic and early postnatal rat brain.

The fatty acid (FA) composition and distribution in a variety of phospholipids (PL) and neutral lipids (NL) at two discrete stages during the embryonic rat brain development were investigated. Over 96% of the FA 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 delivery. Phosphatidylcholine constituted approximately 60% of the total PL pool, phosphatidylethanolamine (PE) 30%, phosphatidylserine (PS) 6%, and phosphatidylinositol (PI) 4%. The diacylglycerols and triacylglycerols constituted 1-2% of the fetal brain lipids. alpha-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 polyunsaturated FA, consisting of arachidonic acid (AA), 22:4n-6 and 22:5n-6, remained unchanged in all the fractions, except in PI, in which the proportion of AA increased. The concentration of docosahexaenoic acid (DHA) increased with age in all the fractions, with the bulk of accumulation accounted for by its increase in PE and, to a lesser extent, in PS. This finding suggests a "DHA accretion spurt" during the last three days of pregnancy.