NUCLEIN OR PURINE METABOLISM 



823 



The same urine would probably have contained about 500 grm. of uric 

 acid. As we should expect, the amount of uric acid in the urine varies with 

 the diet. The following Tables from Bunge give the composition of the 

 urine secreted (1) on a mixed diet, (2) on a diet mainly composed of meat, 

 (3) on a diet mainly composed of bread : 



An attempt has been made to arrive at the amount of uric acid produced 

 endogenously, i. e. from the breakdown of the tissues, from a study of the 

 quantity of uric acid in the urine under varying conditions of food. During 

 starvation, when the man is living on his own tissues, one might expect the 

 uric acid to be increased in consequence of disintegration of the tissues. 

 It has been suggested that the amount of the endogenous uric acid in the 

 urine would be obtained by an analysis of the urine from patients taking 

 a diet free from purine bases, but containing sufficient nitrogen to maintain 

 nitrogenous equilibrium. It is impossible however to arrive at any 

 constant figure for the endogenous uric acid. Even in the entire absence 

 of purine derivatives from the diet, the amount of uric acid increases with 

 the total nitrogenous metabolism. This fact is well shown in the Tables 

 by Folin (already quoted) of the composition of the urine on a low and a 

 high protein diet respectively. Although in each case care was taken to 

 exclude purine-containing bodies from the food, the output of uric acid 

 on the high nitrogenous diet was double as much as on the low diet. All 

 we can say is that uric acid is constantly being derived from the tissue 

 disintegration, but that it varies under different conditions of nutrition as 

 well as under different conditions of activity of the body. 



There are two main conditions which give rise to a marked increase in 

 the output of endogenous uric acid. These are (1) severe muscular activity, 

 (2) febrile states accompanied by increased nitrogenous metabolism. Since 

 both these conditions are associated with an increased breakdown of muscle 

 substance, we may regard the uric acid as derived especially from the 

 hypoxanthine or its precursors, such as inosinic acid, contained in the 

 muscle. 



