NUTRITION OF MICRO-ORGANISMS 



8. PHARMACOLOGY OF p-AMINOBENZOIC ACID 



The toxicity of ^-aminobenzoic acid was studied by C. C. Scott 

 and E. B. Robbins/ who found that it was more toxic to mice and 

 dogs than to rats when given orally, but more toxic to rats than to 

 mice when the sodium salt was given intravenously. The values of 

 LD50 were 2-85, 1-3 and 7-6 g. per kg. for mice, dogs and rats respectively 

 by the oral route, and 4-6 and 2-8 g. per kg. for mice and rats respec- 

 tively by the intravenous route. Oral doses in excess of i g. per kg. 

 generally caused death in dogs, following acute gastro-enteritis and 

 haemorrhage into the small intestine. Acute necrosis of the liver 

 was produced by 2 g. per kg. or more. Rats tolerated 1-4 g. per kg. 

 per day by mouth for a month without ill effects. 



It has been stated, ^ however, that adult rats fed a diet containing 

 3 % of ^-aminobenzoic acid developed enlarged thyroid glands after 

 about a month, but this was not confirmed by C. D. Sullivan and 

 J. W. Archdeacon,^ w^ho gave 7-5 mg. of ;/)-aminobenzoic acid daily for 

 forty-eight days by the intraperitoneal route and could observ^e no 

 change in the weight of the thyroid glands. Body growth was in- 

 hibited, however, and the adrenals were slightly enlarged. 



References to Section 8 



1. C. C. Scott and E. B. Robbins, Proc. Sac. Exp. Biol. Med., 1942, 



49, 184. 



2. A. S. Gordon, E. D. Gk)ldsmith and H. A. Charipper, Endocrinology, 



1945. 37, 223. 



3. C. D. Sullivan and J. W. Archdeacon, ihid., 1947, 41, 325. 



9. p-AMINOBENZOIC ACID IN THE NUTRITION OF 

 2VUCRO-ORGANISMS 



Bacteria requiring p-Axninobenzoic Acid 



The Woods-Fildes theory (page 546) postulated that ;^-amino- 

 benzoic acid was an essential metabqlite of all micro-organisms sus- 

 ceptible to the action of the sulphonamides. Although some of these 

 organisms can synthesise it for themselves others require it pre-formed 

 in the medium before they can grow ; in such instances, ^-amino- 

 benzoic acid is also an essential growth factor. The first micro- 

 organisms shown to require ^-aminobenzoic acid were Clostridium 

 acetohutylicum ^ and Streptohacterium plantarum.^ 



Clostridium acetohutylicum has been used for the microbiological 

 assay of ^-aminobenzoic acid (page 550) and so have Acetohacter 



555 



