IX. mi; I'A HOLISM 45 



thoiiR- aci(,l is lulmiiiisUMvd. Charalampous and Ilc^stcd" note that of the 

 coinpoutuls! elToctivo in iiicivasiiiji; acrlylation of PABA l)y the alloxan- 

 treated rat only A TP, or compounds expected to stimulate ATP synthesis, 

 are effective. Reduced acetylation of PABA in the alloxan-treated rat, 

 then, is due to a relati\e deficiency of ATP, the immediate energy soiwce 

 of the reaction. 



As might be expected from the fact that pantothenic acid, as coenzyme 

 A, is concerned with the acetylation of such compounds as sulfanilamide'-' '^ 

 and choline,'^ pantothenic acid deficiency is accompanied l)y impaired 

 acetylation of PABA in the rat. Riggs and Hegsted'^ found that normal 

 rats acetylate 70% of the amount of PABA excreted in 24 hours after a 

 1-mg. or 2.0-mg. dose of PABA administered intraperitoneally. On the 

 other hand, pantothenic acid-deficient rats acetylate only 50 % of a 1-mg. 

 dose or 37 % of a 2.5-mg. dose similarly administered. Acetylation of PABA 

 is less than normal in thiamine-deficient and riboflavin-deficient rats, 

 but the magnitude of the effect is not so great as in pantothenic acid de- 

 ficiency.^'' Acetylation by riboflavin-deficient rats is not influenced by the 

 administration of pantothenic acid. Differences in acetj^lating ability as a 

 function of diet are only apparent following the administration of amounts 

 of PABA of the order of 1 to 2 mg. At a dose of 10 mg. or more, normal, 

 thiamine-, riboflavin-, or pantothenic acid-deficient rats all acetylate about 

 the same percentage of injected PABA, namelj', about 40 %. 



Dumm and Ralli^^ confirm the effect of pantothenic acid deficiency as a 

 factor in reducing the ability of the rat to acetj'late PABA. ^Male rats on a 

 normal diet, a pantothenic acid-deficient diet, or a pantothenic acid-high 

 diet were found to acetylate a greater percentage of peritoneally injected 

 PABA than female rats on corresponding diets. 



Riggs and Hegsted'^ have studied the acetylation of PABA by normal 

 and pantothenic acid-deficient rats of various body weights after the intra- 

 peritoneal injection of 1 mg. of the amine. Rats weighing about 300 g. 

 acetylate a greater percentage of the PABA administered than do weanling 

 rats of about 40 g. body weight. Young rats show decreased acetylation 

 almost immediately upon withdrawal of pantothenate from the diet. Older 

 animals continue to acetylate PABA normally for at least two months. 

 These latter findings are correlated with the well-known difficulties en- 

 countered in producing vitamin deficiencies in older animals.'^ 



'2 F. Lipmann, J. Biol Chem. 160, 173 (1945). 



" F. Lipmann and X. O. Kaplan, Federation Proc. 5, 145 (1946). 



'* F. Lipmann and X. O. Kaplan, /. Biol. Chem. 162, 743 (1946). 



i» T. R. Riggs and D. M. Hegsted, J. Biol. Chem. 172, 539 (1948). 



" T. R. Riggs and D. M. Hegsted, J. Biol. Chem. 178, 669 (1949). 



'" M. E. Dumm and E. P. Ralli, /. Xutritiori 44, 265 (1951 ). 



'« T. R. Riggs and D. M. Hegsted, /. Biol. Chem. 193, 669 (1951). 



" E. C. Miller and C. A. Baumann, J. Xulrition 27, 319 (1944). 



