190 PTEROYLGLUTAMIC ACID 



suxidine. Repeated production of anemia by bleeding failed to show any 

 difference between the control dogs and those receiving sulfasuxidine. Re- 

 generation of hemoglobin after hemorrhage was rapid even in the presence 

 of 4 % sulfasuxidine. This is in marked contrast to the rat, which develops 

 an impaired capacity to regenerate hemoglobin on a sulfonamide-contain- 

 ing diet. Deficiencies of PGA were obtained by Krehl et al}^ by imposing 

 the stress of another vitamin deficiency. Dogs kept on a niacin-deficient 

 diet were found to respond to a few successive single doses of niacin but 

 then finally failed to respond and died even though niacin was adminis- 

 tered. In each case the animal was allowed to become deficient again before 

 the next dose of niacin was administered. If PGA was included in the diet, 

 the response to niacin was improved and the dog could be alternately 

 treated with niacin and allowed to become deficient again a large number 

 of times. This production of deficiency of PGA by a concomitant nicotinic 

 acid deficiency is reminiscent of the relationship observed between PGA 

 and riboflavin in the rat.^^ 



9. Foxes 



Schaefer et alP found that foxes kept on a purified type of diet develop 

 critical symptoms of PGA deficiency in 7 to 14 weeks. These include ano- 

 rexia, rapid loss of body weight, and reduction of hemoglobin. Total white 

 cell and erythrocyte counts were reduced to approximately 50 % of the 

 normal value. Administration of 0.25 to 1.0 mg. of PGA per kilogram of 

 diet resulted in an increase in hemoglobin, white cells, and growth rate. 

 A yeast preparation containing pteroylglutamic acid conjugate, when fed 

 at a level calculated to give 0.60 mg. of PGA in the form of the conjugate, 

 failed to produce any hematological or growth response. A similar yeast 

 preparation hydrolyzed with kidney enzyme produced a typical increase 

 in hemoglobin level. This shows that the fox, in contrast to all other animals 

 thus far observed, is unable to utilize the PGA conjugates present in yeast. 



It is also interesting that the fox, although taxonomically related to the 

 dog, is so susceptible to PGA deficiency, whereas the dog is quite resistant. 

 Adult foxes as well as growing pups developed PGA deficiency symptoms 

 on the purified diet. There is evidence that an unidentified factor present 

 in fiver is also required by foxes in addition to PGA.^^ 



10. Insects 



Several insects have been observed which require PGA at some stage of 

 their development. Larvae of the mosquito Aedes acgypfn were found by 



*^^ W. A. Krehl, N. Torhet, J. de l;i Iluerga, :uul C A. Elvehjem, Arch. HiiH-hoii. 11, 



363 (1946). 

 8»A. E. Schaefer, C. K. Whiteh:i,ir, and C. A. Elvehjem, Arch. Biochcw. 12, 319 



(1947). 



