584 G ASTRO-INTESTINAL "AUTOINTOXICATION" 



pionic acid appear under similar conditions, except that the two oxy-acids are 

 possibly also formed within the body through cellular metabolism, as they have 

 been found present in the urine independent of intestinal putrefaction. Para- 

 cresol is quantitatively the most important of the urinary phenols, and long con- 

 tinued feeding produces no noticeable effects in rabbits.''* Probably part of the 

 benzoic acid that appears in the urine combined with glycine, as hippuric acid, is 

 derived from intestinal putrefaction.*^ 



The Pressor Bases^" 



Among the products of protein putrefaction are several amines 

 that have marked power to stimulate the sympathetic nervous system 

 and thus to raise the blood pressure, hence resembling epinephrine 

 physiologically as well as chemically. There are also bases derived 

 from amino-acids which stimulate non-striated muscle without raising 

 general blood pressure. The most important of these bases are: 



Phemjl-ethylamine C6H5.CH2.CH0.NH2, 



derived from phenylalanine C6H6.CH2CHNH2.COOH. 



Para-hydroxy-phenyl-ethylamine (tyramine) OH.C6H4.CH>.CH-..XH2 



derived from tyrosine. OH.C6H4.CH2.CHNH2.CbOH. 



Its relation to epinephrine is seen on comparing with the structural formula of 

 the latter (OH)2C6H3.CHOH.CH2NH.CH3 



/NH— CH 

 Beta-iminazolyl-ethylarnine {histamine) CH/^ : 



^N C— CHoiCHo.NH. 



.NH— CH 

 derived from histidine CH/' 



^N C— CH2.CHNH2.COOH 



It will be observed that these are all amines derived from the 

 cyclic amino-acids of proteins by the process of decarhoxylization 

 (loss of CO2). The straight chain amines are much less active 

 physiologically. The lowest amine having any considerable pressor 

 action is isohutylamine, but para'phenylamine is at least five times as 

 active as any aliphatic amine (Barger). Tyramine injected subcutan- 

 eously or intravenously increases blood pressure and slows the pulse 

 rate,''^ resembling epinephrine, but it is onl}^ one-twentieth as active. 

 Histamine causes ordinarily a fall of blood pressure, although it does 

 constrict many peripheral vessels. Capillaries are dilated by his- 

 tamine and Dale and Laidlaw compare it to a capillary i)oison.''^° Its 

 most striking effect is in causing profound contraction of the uterine 

 and bronchial muscle. The relative effects of epinephrine, tryamine 

 and histamine are given by Barbour, as follows : 



*s Denny and Frothingham, Jour. Med. Res., 1914 (31), 277. 



" See Prager, Med. News, 1905 (86), 1025; Magnus-Levy, Munch med. Woch., 

 1905 (52), 21G8. 



*" Full bibliography given by Barger, "The Simpler Natural Bases, "^Mono- 

 graphs on Biochemistry, London, 1914. 



•iSee Hewlett, Proc. Soc. Exp. Biol. Med., 1917 (15), 12. 



""See also Dale and Richards, Jour. Physiol., 1918 (52), 110. 



