METABOLISM OF PHOSPHORYLCHOLINE AND LECITHIN IN NORMAL AND CHOLINE-DEFICIENT RATS

1. 1. The metabolism of phosphorylcholine and lecithin in liver and plasma of normal rats and rats in the early stages of choline-deficiency has been studied. 2. 2. A striking reduction (over 70%) of phosphorylcholine levels in choline-deficient livers and a greatly decreased labelling from 32Pi and [1,2-14C2]choline was found. 3. 3. Levels of lecithin were slightly depressed in choline-deficient livers but there was increased incorporation of 32Pi, [1,2-14C2]-choline and [Me-14C]methionine into liver lecithin. Increased radioactivity from the three precursors was found also in plasma phospholipids. 4. 4. The labelling of phosphorylcholine and lecithin from 32Pi at different time intervals suggested that, in choline-deficient livers, although phosphorylcholine synthesis was depressed, it was not rate-limiting for lecithin formation and that there was, in fact, an increased conversion of 32P-labelled phosphorylcholine into lecithin. 5. 5. The labelling of liver phosphorylcholine and lecithin from [1,2-14C2]choline in the control animals was also consistent with a precursor-product relationship. However in the choline-deficient animals the specific activity of lecithin was almost equal to that of phosphorylcholine in the early intervals after injection of the tracer and it is suggested that [1,2-14C2]choline may, in part, be incorporated into liver lecithin by a pathway independent of phosphorylcholine. 6. 6. The possible relationship between these findings and the accumulation of liver fat in the choline-deficient animals is discussed. © 1969.