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The Relation of Dietary Choline and Methionine to Phospholipid Synthesis in the Rat^1,2,

Department of Animal Science, Agricultural Experiment Station, Auburn University, Auburn, Alabama 36830

Phospholipid synthesis in hepatic tissue from male, weanling rats fed a basal diet deficient in choline and limited in methionine was compared with that in rats receiving the basal diet plus 0.3% choline or 1% methionine or both. Rats fed one of the four diets for 5 days were injected with choline-1,2-¹⁴C. The incorporation of choline into hepatic phospholipids in vivo was dependent upon the level of dietary choline but was independent of the level of dietary methionine. Rats on the choline-deficient diet incorporated two to six times as much labeled choline as rats on the choline-supplemented diet, while rats receiving 1% methionine incorporated three to six times as much label as the choline-supplemented rats. Rats receiving the diet supplemented with both methionine and choline incorporated approximately the same activity as the rats receiving the choline diet. The effect of previous dietary regimen (presence or absence of choline in the diet) on the incorporation of cytidine diphosphate choline and methyl groups from S-adenosyl-L-methionine (SAM) into phospholipids was also studied in vitro. Previous dietary treatment of the donor animals had no effect on the incorporation of either precursor by a microsomal system. However, when a mixture of microsomes and cell supernatant fluid was used as an enzyme source, only one-third to one-half as much activity from the labeled SAM was incorporated into the in vitro system derived from the choline-supplemented rats. This inhibition was alleviated by dialysis of the supernatant fluid.

² A preliminary report of this work was presented before the Fifty-third Annual Meeting of the Federation of American Societies for Experimental Biology in Atlantic City, N. J., 1969.

³ The material presented herein is taken in part from a dissertation submitted to the Graduate School of Auburn University by James H. Haggard in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Present address: Armour and Company, Food Research Division, Oakbrook, Ill. 60521.

Manuscript received 15 January 1970.