VII. ESTIMATION 57 



Kaliaiie and Levy worked out procedures for the estimation of free choline, 

 total water-soluble choline, and total choline. ""^^ 



C. BIOLOGICAL ASSAYS 



The first determination of choline by l)iological assay was based on its 

 acetylation to acetylcholine and on the estimation of the latter b}' \'irtue of 

 its pharmacological action on tissues. An extensive discussion of this pro- 

 cedure has been published by Chang and Gaddum.^" The most satisfactory 

 tissues for the test are the rectis abdominis muscle of the frog, the isolated 

 intestine of the rabbit, and the longitudinal muscle of the leech. The 

 method was used by Abdon^^ for the determmation of acetylcholine and 

 its precursor in tissues and by Fletcher et al.^- in the analysis of a number 

 of foodstuffs for total choline. Accuracy is difficult because of interfering 

 substances such as histamine, potassium salts, and many other physio- 

 logically active constituents of tissues. 



Attempts have been made to develop a biological assay procedure for 

 the determination of the total choline in foods and in other biological 

 materials by comj^arison of the degree of prevention of renal pathology by 

 the test substance and by choline in young rats on a choline-deficient 

 diet.^^' ^^ The method is not particularly sensitive and the interpretation 

 of results is complicated by variations in food consumption and in the 

 composition of the ration. 



D. PHYSICAL ESTIMATION 



The ultraviolet absorption spectrum of choline^* • ^^ is not useful as an 

 analytical tool although advantage is taken of the spectrum of choline 

 reineckate. It has not been possible to utilize other physical properties of 

 choline in its estimation. 



" G. Ducet and E. Kahane, Bull. soc. chim. biol. 28, 79-4 (1946). 



48 E. Kahane and J. Levy, Compt. rend. 207, 642 (1938). 



4' E. Kahane, J. Levj-, and O. Libert, Bull. soc. chim. biol. 27, 65 (1945). 



60 H. C. Chang and J. H. Gaddum, J. Physiol. {London) 79, 255 (1933). 



*' N. O. Abdon and K. Ljungdahl-Ostberg, Acta Physiol. Scand. 8, 103 (1944). 



" J. D. Fletcher, C. H. Best, and O. M. Solandt, Bwchem. J. 29, 2278 (1935). 



" W. H. Griffith and D. J. Mulford, J. A7n. Chem. Soc. 63, 929 (1941). 



" A. Castille and .M. Ruppal, Bull. acad. roy. med. BeUj. 56, 263 (1926). 



" W. Graubner, Z. ges. exptl. Med. 63, 527 (1928). 



