Developmental changes in rat blood choline concentration

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Abstract
Serum choline concentration in the newborn rat is extremely high and declines as the rat matures until adult values are attained at 20 days of age. Rat milk is a rich source of choline. Rat pups denied access to milk had significantly lower serum choline concentrations than did fed littermates. Dietary intake of choline contributes to the maintenance of high serum choline concentrations in the neonatal rat. In vivo choline disappears with a half-life of 70 min. It is converted into betaine, phosphocholine and phosphatidylcholine. The rate of phosphocholine formation is identical in 3 and 10 day old rats (3.3 .mu.mol/h); the rate of betaine formation is slower in younger animals (0.15 .mu.mol/h at 3 days vs. 0.69 .mu.mol/h at 10 days). In vitro choline oxidase activity (choline dehydrogenase [EC 1.1.99.1] and betaine aldehyde dehydrogenase [EC 1.2.1.8]) increased between birth and 40 days of age. The age-related acceleration in choline''s conversion into betaine probably tends to diminish unesterified choline concentration in the rat.