On the biosynthesis of plasmalogens during myelination in the rat. VIII[1]. Incorporation of 1-[1-14C] alkyl-2-acyl-3-sn-glycerophosphoethanolamine with different fatty acids.

The uptake of 14C labelled alkyl chains into the alkenyl chains of plasmalogens was estimated 12, 24, 48 and 72 h after intracerebral administration of different substrates to 14 day-old rats We used as substrates 1-[1-14C] alkyl-3-sn-glycerophosphoethanolamines, containing in the 2-position of the glycerol residue a stearoyl (substrate I), an oleoyl (II), an archidonoyl (III), a 4, 7, 10, 13, 16, 19-docosahexaenoyl (IV) or no acyl residue (substrate V, so-called lysoether phosphatide). 1) If the fatty acid in the 2-position of the substrate is a saturated one (as in experiment I), the recovery of radioactive alkyl chains is relatively high, but their desaturation is very slow and seems not to reach its maximum even after 72 h. 2) If a substrate with an unsaturated fatty acid in the 2-position is applied, the number of radioactive chains (alkyl plus alkenyl) depends on the chain length and/or the number of double bonds in the fatty acids. The desaturation of the alkyl chains, however, reaches its maximum about 48 h after application (except for substrate IV). 3) Not only is the recovery of radioactivity in the glycerophosphoethanolamine lipids by far the highest in experiment V at any time, but also the total activity of the alkenyl chains has already reached a maximum 24 h after application.