REGULATION OF CELL ACTIVITIES 195 



other words, the physiological action of drugs depends, like 

 their chemical reactions, on the stereochemical configuration 

 of their molecules. We thus see why a good working knowledge 

 of organic chemistry is necessary for the biological chemist. 



One of the compounds which has been thoroughly investi- 

 gated is the substance adrenaline. Its specific action can be 

 shown in more or less degree by many substances of allied 

 chemical nature. Its activity resembles the effect of stimula- 

 tion of the sympathetic nervous system, so Barger and Dale 

 have suggested the term " sympathomimetic " for drugs 

 that behave like adrenaline.* 



The main factor in producing the sympathomimetic 'action 

 is an NH 2 group or substituted NH 2 group (NHCH 3 in 

 adrenaline). Thus many amines produce a rise of blood 

 pressure on injection into an animal. The presence of a 

 benzene ring intensifies the activity, if the NH 2 group is 

 separated from the aromatic nucleus by at least one carbon 

 atom. The addition of hydroxyl groups to the benzene ring 

 makes the activity greater. 



The secondary alcohol group intensifies the activity, but 

 it is found that the Isevorotatory substance accounts for all 

 the activity and the dextrorotatory compound is inactive.! 



The ketone CO'CH 2 (NHCH 3 ) 



HO 



HO! 



is much less active than the secondary alcohol 



CHOH'CH 2 (NHCH 3 ) 

 HO, " 



o 



HO 1 



Adrenaline. 



In the above synopsis we see that each portion of the 

 molecule has some effect on the physiological activity, and 

 that comparatively trifling changes caused marked alterations 

 in the activity of the compound. Alkaloids show a similar 

 relation : slight differences in chemical constitution make a 

 great difference in their physiological activity. 

 PITUITARY GLAND. 



This organ, which is composed of three distinct portions, 



* G. Barger and H. H. Dale, Journ. Physiol., 1911, vol. 41, p. 19. 



f A. R. Cushny, Journ. Physiol., 1908", vol. 37, p. 130. 



