Acyl composition and phospholipase activities in plasma membranes isolated from rat embryos.

A subcellular fraction enriched in plasma membranes and relatively poor in other subcellular membranes was isolated from homogenates of rat embryos obtained on the 15th day of gestation. Characterization of this fraction revealed a paucity of stearate, arachidonate and long chain polyunsaturated fatty acids relative to palmitic, oleic, linoleic and linolenic acids, in total phospholipids. Estimation of phospholipase A activity revealed that phospholipase A1 and A2 were present in plasma membranes from rat embryos. A relatively high lysophospholipase activity was also found in the PM-rf, and may be the metabolic basis for the paucity of long chain polyunsaturated fatty acids in the embryo-derived plasma membranes.