186 PTEROYLGLUTAMIC ACID 



although reticulogen is active for Le. citrovorum at very low concentrations, 

 the actual amount of citrovorum factor supplied by the 45 U.S. P. units of 

 reticulogen would correspond to only about 5 7 of CF per day. It would 

 indeed be interesting to see whether the citrovorum factor (folinic acid) 

 would be more effective than PGA under the conditions of this test. 



4. Pigs 



PGA deficiencies in swine have not been observed on either purified or 

 natural diets without the use of intestinal antiseptics. Baby pigs which had 

 been given colostrum for 4 days and then placed on a diet of synthetic milk 

 plus 2 % sulfathalidine (calculated on solids content of the milk) did not 

 develop any signs of PGA deficiency (Johnson et alJ^). The baby pig diet 

 contained 30 % of Labco \dtamin-free casein and 27 % lard. Since subsequent 

 work with swine and previous work with rats have shown that PGA re- 

 quirements are decreased at higher protein levels, it seems possible that the 

 failure to produce any PGA deficiency as measured by growth or blood pic- 

 ture may be a reflection of the high protein level used. 



With adult pigs blood changes have been produced by feeding of purified 

 diets containing sulfonamides. Cartwright et aU^ fed a diet containing 26 % 

 of Labco vitamin-free casein and 2 % of sulfasuxidine. After 120 days growth 

 almost stopped and marked alopecia developed, especially over the flanks 

 and rump. A normocytic anemia developed, and the hematocrit dropped to 

 21 %. Administration of biotin produced no change in the skin condition. 

 Administration of 1 ml. of purified liver extract for 9 days produced a retic- 

 ulocyte response with a peak of 9.4%, a marked growth response of 30 

 kg. in 50 days, and restoration of a normal hair coat. Four animals which 

 received sulfasuxidine and crude casein in place of the vitamin-free casein 

 were normal in all respects. In this particular experiment it appears that 

 vitamin B12 was producing a response on a diet supposedly deficient in PGA. 



In a subsequent paper these same workers,'^^ using a larger number of 

 animals, found that pigs on this same diet containing Labco \itamin-free 

 casein and sulfasuxidine would respond only partially to refined liver extract 

 but completely to PGA. The reticulocyte peak with PGA varied between 

 4 and 16% and that with Hver extract between 5 and 8%. Substitution of 

 crude casein for vitamin-free casein reduced the severity of the anemia, and 

 spontaneous remissions with broad reticulocyte responses sometimes oc- 

 curred. Reduction of the crude casein level from 26 to 10 % made the ane- 

 mia more severe. 



74 B. C. Johnson, M. F. James, and J. L. Krider, J . Animal Sci. 7, -186 (1948). 



'^ G. E. Cartwrifrht, M. M. Wintrohe, and S. Humphreys, J. Lab. Clin. Med. 31, 423 



(1946). 

 ^« G. E. Cartwright and M. M Wintrobe, Proc. Soc. Expll. Biol. Med. 71, 54 (1949). 



