Phospholipids in the liver of the pregnant rat: changes in fatty acid content and composition

Pregnancy in the rat was associated with changes in hepatic phospholipids. All changes returned to the prepregnancy levels 2 to 3 weeks postpartum. The total phospholipid content was reduced significantly, mainly representing a reduction of phosphatidylcholine, -ethanolamine, and lysophosphatidylcholine fractions. Hepatic fatty acid content was also reduced and the composition was modified since both saturated and unsaturated acyl components were decreased with more pronounced changes in unsaturated acids. Total liver saturated fatty acids with 14 to 16 carbon atoms remained unaltered; stearic acid was reduced and arachidic and lignoceric acids were elevated. Among unsaturated fatty acids, palmitoleic, oleic, eicosatrienoic, arachidonic, eicosapentaenoic, and docosapentaenoic were decreased, docosatrienoic and docosahexaenoic were raised, whereas eicosaenoic and eicosadienoic did not change. In the phosphatidylcholine and -ethanolamine fractions, unsaturated acyl components also showed significant reduction. By and large they reflected the fatty acid changes occurring in total liver with the exception of the docosahexaenoic acid which was diminished in both fractions. The overall effect of pregnancy thus indicated a modification in unsaturated fatty acid content leading to the construction of less fluid membranes which may be responsible for the reduced enzyme activity of the endoplasmic reticulum.