VI. ESTIMATION 629 



However, such assays have less significance in terms of the content of 

 pantothenic acid itself. 



1. Rat Growth Assays 



Satisfactory assays for pantothenic acid activity may be made by re- 

 moving pantothenic acid from any of the good, highly purified diets for 

 rats in use today. The pantothenic acid activity of crude materials may 

 then be calculated by comparing the growth obtained with such materials 

 with standard growth curves obtained by feeding graded levels of crystalline 

 calcium pantothenate. 



As an example of the use of this principle, a successful rat growth assay 

 was used by Wisconsin workers^ in 1951 to determine the activity of bound 

 forms of pantothenic acid. Total pantothenic acid activity of certain sam- 

 ples of liver, yeast, wheat bran, and rice bran was greater than indicated 

 by microbiological assay. A few other laboratories have also used rat 

 assays,^-'' but older rat assays now need modification because of newer 

 vitamins which have since been discovered. 



2. Chick Growth Assays 



Assays for pantothenic acid activity may be made with chicks by the 

 same general method as that used with rats. Chick assays have the ad- 

 vantage over rat assays of being somewhat less expensive and of shorter 

 duration. For instance, Hegsted and Lipmann,^ in 1948, measured the 

 pantothenic acid content of coenzyme A by using a purified-type diet low 

 in pantothenic acid. Day-old chicks were fed a commercial chick mash for 

 4 days and then placed on the pantothenic acid-low diet. After a short 

 depletion period the chicks were divided into uniform groups for assay 

 purposes. The length of the actual assay period was only 8 to 10 days. 



Animal assays, especially chick assays, have been very useful as a stand- 

 ard in the development of improved microbiological methods for panto- 

 thenic acid. This is true because the animal can utilize bound forms of 

 pantothenic acid which usually are not available to bacteria unless re- 

 leased by special techniques. ^-^^ 



5 H. Lih, T. E. King, H. Higgins, C. A. Baumann, and F. M. Strong, J. Nutrition 



44, 361 (1951). 

 « J. S. D. Bacon, G. N. Jenkins, and J. O. Irwin, Biochem. J. 37, 492 (1943). 

 ' N. B. Guerrant, M. G. V^avich, and O. B. Fardig, Ind. Eng. Chem. Anal. Ed. 17, 



710 (1945). 

 8 D. M. Hegsted and F. Lipmann, J. Biol. Chem. 174, 89 (1948). 

 s D. Pennington, E. E. Snell, H. K. Mitchell, J. R. McMahan, and R. J. Williams, 



Univ. Texas Publ. 4137, 14 (1941). 

 '0 A. L. Neal and F. M. Strong, /. Am. Chem. Soc. 65, 1659 (1943). 

 11 A. L. Neal and F. M. Strong, Ind. Eng. Chem. Anal. Ed. 15, 654 (1943). 



