Incorporation of CDP-choline (methyl-14C) into lecithin or adult rat liver mitochondria and microsomes.

Incorporation of CDP-choline (Methyl-14C) into liver microsomes and mitochondria was studied in vitro. Labelling of a total homogenate and subsequent separation of subcellular fractions showed that radioactivity was present in both microsomes and mitochondria, the highest specific activity being attained by microsomes. Chase experiments disclosed any transfer of label from one fraction to the other. Individual incubation of microsomes and mitochondria indicated that both fractions were able to incorporate label into phosphatidyl choline independently. The addition of increasing amounts of microsomes to mitochondria enhanced incorporation in proportion to the amount of microsomes added. If 10% contamination of mitochondria with microsomes is assumed, extrapolation of the curve back to zero contamination shows that mitochondria seem to have an autonomous capacity to incorporate the precursor into phosphatidyl choline.