Synthesis of C20 and C22 polyunsaturated fatty acids by the placenta of the sheep.

Incubation in vitro of sheep placental homogenates with [1-14C] oleic, linoleic and linolenic acids resulted in extensive amounts of radioactivity becoming associated with C20 and C22 polyunsaturated fatty acid products. The fatty acids of the fetal plasma displayed substantial levels of both C20 and C22 polyunsaturated fatty acids, including the n-9 eicosatrienoic fatty acid associated with essential fatty acid deficiency, but extremely low levels of linoleic and linolenic acids. A role for the placenta in the provision to the fetus of a range of C20 and C22 polyunsaturated fatty acids derived from C18 fatty acid precursors is implicated.