A chemical method for the determination of free choline in plasma.

نویسندگان

  • H D APPLETON
  • B N LA DU
  • B LEVY
  • J M STEELE
  • B B BRODIE
چکیده

In the course of studies on the intermediary metabolism of choline, a large number of determinations of free choline in plasma was required. As none of the methods hitherto described was satisfactory for our purpose, a sensitive chemical method was developed by which the free choline could be accurately determined by using small amounts of plasma. The chemical methods most commonly used for the estimation of choline involve (a) precipitation with Reinecke salt to yield choline reineckate, followed by calorimetric measurement of the complex (l-lo), and (6) precipitation with potassium triiodide to yield choline periodide (choline enneaiodide) with subsequent determination of the iodine (11-15). In both of these procedures the choline derivative must be washed free of excess reagent before it can be assayed, and small amounts are lost in the washing of the precipitate. In the determination of mg. quantities of choline this loss is insignificant, but with small amounts of choline the loss becomes appreciable. For this reason these procedures are not well suited for the estimation of free choline in plasma. It was observed in this laboratory that choline periodide is soluble in ethylene dichloride and in this solvent exhibits an ultraviolet absorption spectrum which differs markedly from that of free iodine (Fig. 1). This permits the measurement of choline periodide in the presence of free iodine adsorbed on the surface of the precipitated complex and thus eliminates the need for washing the precipitate. With this principle, a method has been developed which permits the estimation of as little as 5 y of choline. This procedure has been applied to the estimation of free choline in plasma.

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عنوان ژورنال:
  • The Journal of biological chemistry

دوره 205 2  شماره 

صفحات  -

تاریخ انتشار 1953