Tissue Choline Studied Using a Simple Chemical Assay

Abstract: An enzymatic-radioisotopic assay was used to measure free choline in unextracted tissue. The lowest concentration of free choline in any tissue studied was present in human cerebrospinal fluid (mean, 5.7 μM; range, 1.8–31.2 μM). A postmortem increase in concentration of free choline occurred in blood (O.2 nmol/min ml), kidney (13 nmol/min·g), and liver (22 nmol/min·g) of mice. The concentration of free choline in these tissues was estimated by extrapolation to be 5, 77, and 29 nmol/g (or ml), respectively. Several treatments were found to increase the concentration of free choline. For example, intraperitoneal administration of choline or 2-amino-2-methyl-propanol (a choline oxidase inhibitor) induced an increase in the level of choline in blood, kidneys, liver, and brain of mice, and administration of 2-dimethylaminoethanol (deanol) caused an increase in kidney and liver choline. The level of choline in blood was increased when rats were treated orally with either antibiotics or esters of choline such as phosphorylcholine, glycerylphos-phorylcholine, laroylcholine, or propionylcholine. The results show that the concentration of free choline may be regulated by intestinal metabolism, availability of esterified precursors, and activity of enzymes that metabolize choline.