86 MEDULLA 



exposure to the air is also due to their content of dopa. Epi- 

 nephrine, too, may be oxidized in the presence of certain oxi- 

 dases (such as that found in the ink-bag of the cuttle fish, 

 {Sepia officinalis) or in toadstools) to give a black pigment 

 resembling the natural melanin found in the skin. 466 



In view of the above described reactions, it has been as- 

 sumed that epinephrine, tyrosine, phenylalanine, or dopa, are 

 precursors of the melanin pigment of the skin. However, in 

 considering the chemical theories which have been elaborated 

 to account for the abnormal deposition of melanin in the skin 

 of persons afflicted with Addison's disease, it must be remem- 

 bered that the characteristic pigmentation also occurs in cases 

 in which the medulla appears to be normal. This would in- 

 dicate that disease of the cortex is primarily responsible for 

 the pigmentation and that any abnormalities in epinephrine 

 metabolism must be only secondarily involved (c/. Chapter 

 XXI). 



OTHER COMPOUNDS RELATED TO EPINEPHRINE 



The important pharmacological properties of epinephrine 

 have led chemists to prepare a number of related compounds 

 some of which have interesting actions, similar to those of 

 epinephrine. None of these has, however, seriously rivalled 

 the natural product and we need only refer to them here. 

 Besides ephedrine, a closely related naturally occurring com- 

 pound, the most important of these compounds are dihydroxy- 

 phenylethanolamine (arterenol) or epinephrine without the 

 methyl group and dihydroxyphenylpropanolamine (homo-ar- 

 terenol). Of interest in connection with the last named com- 

 pound is the fact that its levo-rotatory isomer is over 30 times 

 as active as the dextro-rotatory form. The study of numerous 

 synthetic and natural products related more or less to epineph- 

 rine has formed an interesting contribution to our knowl- 

 edge of the relation of chemical structure to biological activ- 

 ity 35, 36,204, 284 



