IV. BIOCHEMICAL SYSTEMS 421 



With tho rapkl U'chiiolojiical development and the iiicioased consump- 

 tion, the original price of $12,r)00 per gram came down to about $300 per 

 gram in the form of crystals and $50 per gram in the form of low concen- 

 trates (1953). 



Even with this low price, \dtamin B12 remains the highest priced organic 

 compound on the open market. Therapeutically, however, vitamin B12 

 cannot be considered to be an expensive vitamin; the high clinical dose of 

 30 7 costs less than one cent in the form of the crystals. 



D. PURITY OF THE COMMERCIAL PRODUCT 



The requirements governing the purity of commercial vitamin B12 are 

 described in U.S.P. XIV, p. 6G0 (official from November 1, 1950); for the 

 official activity assay see third supplement p. 15 (January 1952). 



IV. Biochemical Systems 



THOMAS H. JUKES and WILLIAM L. WILLIAMS 



A. VITAMIN B12 AND NITROGEN METABOLISM IN ANIMALS 



A deficiency now knowTi to be that of vitamin B12 was shown to be 

 intensified in rats and chicks by raising the protein level of the diet.^-^ 

 These early experiments were an indication of an involvement of vitamin 

 B12 in the metabolism of compounds of nitrogen. Further relationships were 

 reported in 1946 by Zucker and Zucker,^ who found that rats on all-vege- 

 table diets had high blood-urea levels and enlarged kidneys, and that 

 stoppages in the urinary tract leading to hydronephrosis sometimes oc- 

 curred. The feeding of liver abolished the symptoms and led to normal 

 growth. Cary and Hartman'* also found that rats which had been for con- 

 siderable periods of time on a diet without the unidentified factor (X) had 

 kidnej^s which were much heavier than those of their much larger sex-litter 

 mates recei\'ing the factor. In a later publication^ Zucker and Zucker de- 

 scribed high blood non-protein nitrogen and urea levels at the time when 

 the animals showed the most marked signs of deficiency. McGinnis and 



1 C. A. Gary, A. M. Hartman, L. P. Dryden, and G. D. Likely, Federalion Proc. 5, 



128 (1946). 

 = D. Whitson, H. W. Titus, and H. R. Bird, Poultry Set. 25, 143 (1946). 

 ^T. F. Zucker and L. M. Zucker, yibstr. Papers 110th Meeting, Ar7i. Chem. Soc. 



p. 7B (1946). 

 * G. A. Gary and A. M. Hartman, Yearbook Agr. 1943-1947, U. S. Dept. Agr. p. 779 



(1947). 

 6 L. M. Zucker and T. F. Zucker, Arch. Biochem. 16, 115 (1948). 



