40 P-AMINOBENZOIC ACID 



or probably more correctly folinic acid, as recently reviewed by Shive,^^ 

 is concerned with purine synthesis. Thus it would appear that dietary PABA 

 is a precursor of folic or folinic acid which is essential for the synthesis of 

 the purine portion of coenzyme A. Coenzyme A is visuahzed as the form in 

 which pantothenic acid is retained. Pantothenic acid, then, rather than 

 PABA emerges as the factor most directly concerned with normal pigmenta- 

 tion of fur or hair. Obviously, any break in the postulated sequence of 

 events, such as dietary restriction of pantothenic acid, dietary restriction 

 of folic acid combined with the administration of a poorly absorbed sul- 

 fonamide, the feeding of hydrociuinone, or other bacteriostatic agent, as 

 well as dietary imbalance of B vitamins (possibly by inositol), may be ex- 

 pected to cause achromotrichia. The condition then will respond to what- 

 ever measure will restore the normal sequence of events. Some suggestions 

 with respect to practical means by which ample tissue stores of pantothenic 

 acid (as coenzyme A or other combined form) might be achieved as a 

 possible means of combating achromotrichia involve (1) administration of 

 LBF (Lactobacillus hulgaricus factor, ^^) a compound intermediate in struc- 

 ture between pantothenic acid and coenzyme A; (2) administration of large 

 amounts of pantothenic acid along with "caronamide"^^ or "benemide"^^ 

 to decrease the renal elimination of the vitamin along the lines studied b^^ 

 Roholt and Schmidt ;^^ and (3) administration of repository forms of panto- 

 thenic acid alone or as in (2). 



In rats fed certain sulfonamides such as sulfaguanidine (but not sulfaniHc 

 acid or guanine or succinylsulfathiazole) hyperemia and enlargement of 

 the thyroid occur, according to MacKenzie et al.^^ The thyroid hyperplasia 

 is accompanied by a decreased food intake, a lessened rate of body growth 

 and development, and a lessened basal oxygen consumption. This thyroid 

 effect of sulfaguanidine is not increased with PABA, but, on the contrary, 

 PABA actually enhances the effect. ^^ The effect of PABA in inhibiting 

 the thyroid was confirmed by Astwood,^'' who found that of the three iso- 

 meric aminobenzoic acids PABA, the only one known to occur naturally, 

 is the most active. Thiouracil and PABA were compared as antithyroid 



^^ W. Shive, in Vitamins and Hormones, 9, 76 (1951). 



90 E. E. Snell, G. M. Brown, V. J. Peters, J. A. Craig, E. L. Wittle, .J. .\. Moore, 



V. M. McGlohon, and O. D. Bird, /. Am. Chem. Soc. 72, 5349 (1950). 

 " K. H. Beyer, A. K. Miller, H. F. Russo, E. A. Patch, and W. F. Verwey, Am. J. 



Physiol. 149, 355 (1947) 

 '2 K. H. Beyer, H. F. Russo, E. K. Tillson, A. K. Miller, W. F. Verwey, and S. R. 



Gass, Am. J. Physiol. 166, 625 (1951). 

 " K. Roholt and V. Schmidt, Scand. J. din. Lab. Invest. 3, 108 (1951). 

 3' J. B. MacKenzie, C. G. MacKenzie, and E. V. McCollum. Science 94, 518 (1941). 

 95 C. G. MacKenzie and J. B. MacKenzie, Endocrinology 32, 185 (1943). 

 flMC. B. Astwood, ./. Pharmacol. Exptl. Therap. 78, 79 (1943). 



