Metabolism of Thymine 



237 



114 (2074) 



Experiments on the metabolism of thymine. 



By HARRY J. DEUEL, JR., and LAFAYETTE B. MENDEL. 



[From the Sheffield Laboratory of Physiological Chemistry in 

 Yale University, New Haven, Conn.] 



The recent demonstration 1 of the readiness by which thymine 

 could be oxidized to urea, pyruvic acid and acetol by such mild 

 reagents as Fe(OH) 3 and -NaHC0 3 at room temperature re- 

 newed our interest in the metabolism of this pyrimidine in the 

 body. 



When 3 gram doses were fed to a small dog (5 kilo), it 

 was possible to isolate approximately one gram of pure thymine 

 from the urine on the following day although none was re- 

 covered after administration of the same amount to a large dog 

 (12 kilo). When 3 grams of thymine were given to the same 

 small animal in daily amounts of 0.25 gram over a period of 

 12 days, it was apparently utilized; for none could be crystal- 

 lized out of the combined urines of the experimental days, nor 

 was any change in the quantity of non-urea nitrogen noted. 

 The dogs were kept upon constant adequate diets. Experiments 

 on other animals are now in progress. 



In every case when thymine was administered, there was 

 an increase in the urea output, suggesting that some of this 

 pyrimidine was metabolized. Attempts to isolate thymine from 

 150 liters of normal human urine were unsuccessful, thus in- 

 dicating that under ordinary conditions of diet, thymine does 

 not escape physiological conversion. 



Whether thymine ordinarily is destroyed as such in the body 

 or whether still in the nucleoside combination is uncertain; 

 the present experiments suggest that the animal organism is able 

 to convert the pyrimidine to urea when it is uncombined. 



The observation of Sweet and Levene 2 that thymine causes 

 diuresis was confirmed when large doses were given; apparent- 

 ly the extent of its diuretic action is dependent upon the amount 

 administered. 



i Johnson, T. B., and Baudisch, O., Jour. Amer. Cliem. Soc, 1921, xliii, 

 2670, 



2 Sweet, J. E., and Levene, P. A., Jour. Exp. Med., 1907, ix, 229. 



