Formation of 8,11,14-octadecatrienoic acid (18:3 n-4) from naturally occurring unique fatty acid, 9,12-hexadecadienoic acid (16:2 n-4), in animal cell cultures.

9,12-Hexadecadienoic acid (16:2 n-4), present in small amounts in fish oils as a naturally occurring unique fatty acid, was incorporated into the phospholipids in rat liver BRL-3A cells to a similar extent as linoleic acid (18:2 n-6). 11,14-Octadecadienoic acid (18:2 n-4) and 8,11,14-octadecatrienoic acid (18:3 n-4) were detected in the cellular lipids of BRL-3A cells when incubated in a medium supplemented with 16:2 n-4 methyl ester. The cellular levels of these acids increased in parallel with 16:2 n-4 methyl ester added to the medium. These compounds were probably formed through conversion from 16:2 n-4 to 16:3 n-4 by delta 6 desaturation, and then 18:3 n-4 was produced by elongation, and part of the surplus 16:2 n-4, not desaturated to 16:3 n-4, elongated to 18:2 n-4. These results suggested that 16:2 n-4 was desaturated by delta 6 desaturase in vitro. It was also shown that 16:2 n-4 inhibited arachidonic acid synthesis from exogenous linoleic acid in BRL-3A cells as efficiently as alpha-linolenic acid (18:3 n-3).