Role of phospholipids in the development of the hepatic endoplasmic reticulum associated with drug metabolism.

During development from fetal to adult age in the female rat the rapid increase of hepatic drug metabolizing activity was paralleled by changes in the production of membrane bound phospholipids. Microsomal phosphatidylcholine synthesis was raised in particular, and was associated with an enhanced activity of S-adenosyl-L-methionine:microsomal phosphatidylethanolamine methyl transferase. This enzyme is responsible, in part, for phosphatidylcholine production by stepwise methylation. Phospholipid acyl components such as various unsaturated fatt acids also showed a sharp rise during development. These results demonstrated that maturation of the hepatic endoplasmic reticulum was correlated with an increased production of phosphatidylcholine that contained greater amounts of unsaturated fatty acids. It is therefore suggested that during maturation phospholipids are not only essential in providing the structural units of the membranes but they also act as organizers of enzyme function.