CHEMISTRY OF EPINEPHRINE 85 



an animal. This formation of an epinephrine-like substance 

 did not occur when an emulsion of the gland was used and 

 hence is a property of the intact cell. The addition of other 

 substances, related structurally to epinephrine, such as dopa, 

 tyrosine, hordenine, phenylalanine, or phenylethylamine did 

 not result in the formation of an epinephrine-like product. It 

 would appear from these experiments that the adrenal medulla 

 forms epinephrine from tyramine. The latter substance, ac- 

 cording to Schuler and Wiedemann, is formed in the kidney 

 by decarboxylation of tyrosine. 



THE DOPA REACTION 



The pigmentation observed in Addison's disease has been 

 attributed by Bloch to an abnormal metabolism of epinephrine 

 or its precursors. Bloch 63 showed that an isolated piece of 

 skin if soaked in dioxyphenylalanine (Dopa) assumes a pig- 

 mented form similar to that observed in Addison's disease. 

 Since dopa is closely related chemically to epinephrine and 

 may be considered as a precursor of epinephrine in the body, 

 Bloch assumed that disease of the medulla, by preventing the 

 formation of epinephrine from its assumed precursor, dopa, 

 allows the latter to discolor the skin. This discoloration of 

 the skin is assumed to be brought about by a specific enzyme 

 (dopase) which converts dopa into melanin. 



Raper 36 has studied the reaction whereby tyrosine is con- 

 verted to dopa which on further oxidation yields an indole 

 carboxylic acid which can be transformed into dihydroxyin- 

 dole, 



H0 M — II 

 H0 \/\ / 



N 

 H 



which in turn condenses to a black pigment similar to the 

 melanin of the skin. The black appearance of bean pods on 



:#* 



, 



