CREATIN AND CREATININ 179 



The Fate of Administered Creatin or Creatinin 



A number of investigators have attacked this problem. The experi- 

 ments of Myers and Fine (e) (1913) are fairly representative. These ob- 

 servers found that when creatin was injected into rabbits a small portion 

 was deposited in the muscles, and from 25 to 80 per cent, depending on 

 the amount injected, could be recovered from the urine. When creatinin 

 was administered an average amount representing 80 per cent of that 

 injected was found in the urine and the remainder was deposited in the 

 muscles. When creatin was fed to man a slight increase in creatinin 

 elimination occurred which accounted for from 3 to 4 per cent of the in- 

 gested substance ; from to 39 per cent, again depending upon the amount 

 administered, appeared in the urine unchanged (Myers and Fine (/t), 

 1915). Many of the other investigators obtained similar results. See 

 Folin (e) (1906), Klercker (a) (&) (1906, 1907), Wolf and Shaffer, Van 

 Hoogenhuyze and Verploegh (&) (1908), Pekelharing and Van Hoogen- 

 huyze (&) (1910.), Foster and Fisher, Towles and Voegtlin, Folin and 

 Denis (a) (1912) and Krause. 



Summarizing, it may be said that when creatinin is administered it is 

 excreted almost quantitatively, whereas creatin is only partly excreted, 

 the major portion being probably destroyed in the body. Only a small 

 percentage of the administered creatin is excreted as creatinin. There 

 is no evidence that creatin is converted into urea. On a high protein 

 diet a smaller amount of administered creatin is retained than on a low 

 diet. According to Krause (&) (1913) children are less able to destroy 

 creatin than adults. 



Gibson and Martin observed that creatin was promptly excreted when 

 administered to patients suffering from progressive muscular atrophy. 



Resume 



The creatin content of muscle is fairly constant for a given species of 

 animal under uniform conditions of diet. 



Muscle creatin is diminished during carbohydrate privation. This 

 change is ascribed to the loss of creatin in the urine. 



The normal excretion of creatin by children and young animals in 

 general is probably due to their relatively high planes of metabolism and 

 their small reserves of glycogen. In the absence of carbohydrate, fat, 

 and protein to a lesser extent are called upon to supply the body require- 

 ments; under these circumstances muscle tissue is disintegrated, creatin 

 is liberated and excreted in the urine. 



The precursor of creatin has not been definitely established. Creatinin 



