The heterogeneity of the glycerophosphate fraction of rat liver

Zilversmit, Entenman & Chaikoff (1948) found that in the liver of the dog, after injection of 3Ps, a fraction rich in glycerophosphate had specific activity-time curves (S.A.*/t) which indicated that glycerophosphate is a precursor of lecithin. Popjak & Muir (1949) obtained similar evidence in support of this view from comparison of the S.A./t curves of a 'glycerophosphate' fraction and those of total phospholipin in rat liver. These conclusions were based on the criteria proposed by Zilversmit, Entenman & Fishler (1943) for the relationships of the S.A./t curves of a precursor of the ultimate com- pound. * S.A. =specific activity (% injected 32P/mg. P).