Developmental changes in the levels of molecular species of triacylglycerol that contain docosahexaenoic acid in adipose tissue of the chick embryo

Triacylglycerols from the initial yolk and from the adipose tissue of the chick embryo were subjected to high-performance liquid chromatography in the silver ion mode to resolve molecular species of triacyl-glycerol on the basis of the degree of unsaturation. A total of 12 such species was resolved from the yolk samples, with only one of these species containing docosahexaenoic acid. In contrast, 17 species were resolved from adipose tissue at day 12 of embryo development, of which 8 contained docosahexaenoic acid. The major species containing this fatty acid consisted of docosahexaenoic acid in combination with palmitic and oleic acids. The amounts of the species consisting of C 16 and C 18, fatty acids in the adipose tissue increased continuously from day 12 until just before hatching at day 19 and then decreased slightly over the hatching period. In contrast, the amounts within the adipose depot of the species containing docosahexaenoic acid reached a maximal level by day 16 and then decreased dramatically to almost undetectable levels during the hatching period. The possibility that adipose tissue triacylglycerol in the chick embryo may function as a temporary store of docosahexaenoic acid for subsequent delivery to the developing neural tissues is suggested.