364 ASCORBIC ACID 



4. Administration of 100 mg. of ascorbic acid by intravenous injection 

 and determination of the urinary excretion during a period of 3 hours. A 

 normal, well-saturated person usually will excrete 50% of the test dose; a 

 depleted person will excrete 15% or less of the test dose; and a scorbutic 

 person will excrete less than 5 % of the test dose.-^ 



These tests indicate only that a person's tissues are saturated or un- 

 saturated. Since the kidney will reabsorb most of the vitamin when the 

 tissues are at all unsaturated, the test cannot give satisfactory evidence of 

 the degree of unsaturation. These tests cannot make or confirm a diagnosis 

 of scurvy. The results can be only compatible or incompatible with such a 

 diagnosis. 



5. Intradermal Test with Dichlorophenolindophenol 



This test, using the rate of disappearance (i.e., reduction) of 0.01 ml. of a 

 solution of 2 , 6-dichlorophenolindophenol (2 mg. to 4.9 ml. of water) in- 

 jected intradermally, has been proposed as an indicator of vitamin C 

 tissue saturation. There are too many reducing agents other than vitamin C 

 in the skin to allow for any accuracy in diagnosis of ascorbic acid deficiency 

 by this method.^"' *^ 



6. Tests for "Tyrosyl Derivatives" 



Sealock and Silberstein^^ showed that homogentisic acid, p-hydroxy- 

 phenylpyruvic acid, and p-hydroxyphenyllactic acid are excreted by scor- 

 butic guinea pigs when the animals are fed tyrosine. These intermediate 

 metabolites are excreted by ascorbic acid-deficient premature infants^^ 

 and scorbutic adult human beings also^^ when given tyrosine. Infants are 

 fed 1 to 5 g. and adults 15 to 20 g. of tyrosine daily. Twenty-four-hour 

 urine specimens are analyzed for the compounds mentioned above by the 

 method of Medes,^^ and for reducing substances, mainly p-hydroxyphenyl- 

 pyruvic acid, by the reduction of phosphomolybdic acid. After the ad- 

 ministration of vitamin C, the amount of "tyrosyl derivatives" excreted is 

 greatly reduced. There is considerable question whether the administration 

 of folic acid will cause a similar diminution in the tyrosyl derivatives in 

 scorbutic human beings.^^- " Apparently where such a diminution has been 



28 E. P. Ralli and S. Sherry, Medicine 20, 251 (1941). 



soH. G. Rapaport and S. Miller, /. Pediat. 15, 503 (1939). 



31 H. G. Poncher and C. H. Stubenrauch, Jr., /. ,4m. Med. Assoc. Ill, 302 (1938). 



32 R. R. Sealock and H. E. Silberstein, /. Biol. Chem. 135, 251 (1940). 



" S. Z. Levine, E. Marples, and H. H. Gordon, J. Clin. Invest. 20, 199 (1941). 



3* W. F. Rogers and F. H. Gardner, J. Lab. Clin. Med. 34, 1491 (1949); 28, 806 (1949). 



36 G. Medes, Biochcm. J. 26, 917 (1932). 



36 C. D. Govan, Jr., and H. H. Gordon, Science 109, 332 (1949). 



37 J. E. Morris, E. R. Harpur, and A. Goldbloom, J. Clin. Invest. 29, 325 (1950). 



