NITROGENOUS BASES DERIVED FROM GUANIDINE 195 



In the urine the anhydride of creatine, Creatinine, is an important 

 constituent: 



/N.CH 3 .CH 2 .COOH /N.CHs.CHs 



HN = C< HN = C< I + H 2 O 



X NH 2 X NH CO 



As a rule creatine itself is not found in mammalian urine, although 

 it replaces creatinine in the urine of birds and is a normal constituent 

 of the urine of young children. In women creatine occurs in the urine 

 immediately after menstruation and occurs in large amounts in the 

 urine during the involution of the uterus which follows delivery. It is 

 considered probable by Folin and others that the creatinine in urine is 

 not derived from the creatine of the muscles but represents a product 

 of the catabolism of protoplasm. Creatine administered by mouth in 

 small doses does not appear in the urine either as such or as creatinine. 



Neither urinary creatinine nor the creatine in muscles is increased 

 by muscular work, but the creatine content of muscles appears to be 

 connected with their Tonus or degree of moderate contraction when at 

 rest. Thus standing at "attention" in a military position increases 

 the urinary creatinine while a long march does not. On the other 

 hand if, as much of the evidence seems to indicate, urinary creatinine 

 is not derived from the creatine of muscles but from the "wear and 

 tear", of tissues this result may merely indicate that standing at 

 "attention" involves more destruction of muscular tissues than the 

 performance of muscular work. 



Creatine is one of the relatively few substances which stimulate the 

 gray matter or Neurones of the cerebral cortex. The customary 

 stimulants for nerve-fibers, calcium-precipitating substances, barium 

 chloride and so forth, have no action upon nerve-cells. Creatine is 

 devoid of stimulating action upon nerve-cells but when applied to the 

 motor areas of the cortex, it throws the animal into convulsions. This 

 may be connected with the fact that the convulsions which accompany 

 Eclampsia, a metabolic disease of pregnancy, are heralded by a sharp 

 rise in the creatine output in the urine. 



Creatinine may be detected by Jaffe's Reaction, which consists in the 

 red color produced by creatinine in alkaline solutions when Picric Acid 

 is added. The color is due to Picramic Acid which is formed by reduc- 

 tion of picric acid. This reaction is employed for the quantitative 

 estimation of creatinine. Creatinine also gives a ruby-red color with 

 Sodium Nitroprusside in alkaline solution (Weyl's Reaction). 



Creatine may be converted into creatinine by boiling with dilute 

 hydrochloric acid, or it may be determined directly by utilizing the 

 pink coloration which it yields with Diacetyl. 



It should be noted that creatine is closely related to Arginine, which 

 is the only product of protein hydrolysis that contains a guanidine 

 radical : 



/CH 3 



/NH.CH 2 .CH 2 .CH 2 .CH(NH 2 )COOH /N< 



HN = C< HN = C< X CH 2 COOH 

 X NH 2 X NH 2 



Arginine. Creatine. 



