THE INFLUENCE OF PYRIMIDINES UPON THE URINARY EXCRETION OF THIAMINE AND PYRAMIN*. t

The urinary excretion of t,hiamine and pyramin was studied in normal young men who were maintained on an essentially constant thiamine intake (4). It was noted that the small day to day variations in the urinary excretion of pyramin were not directly related to the slight daily changes in the dietary thiamine intake. That finding raised the question as to whether the pyrimidines related to thiamine present in the diets might be the cause of this variation. The food used in that study was composed primarily of preserved products such as dehydrated potatoes, canned meat, canned vegetables, and dried fruit. According to presently accepted theory, the treatment to which these foods were subjected results in the cleavage of the thiamine molecule with the liberation of the pyrimidine and thiazole groups. This could produce a variable pyrimidine content of the diet, depending upon the amount of thiamine that was destroyed during the processing and preparation of the food. A second factor causing some concern in our pyramin studies was the occurrence of a so called “dietary blank.” Urinary pyramin excretions for various levels of thiamine were secured after the subjects had become adjusted to the particular thiamine intake levels. Extrapolation of these values to a zero thiamine intake indicated an excretion of about 70 y per day (4). This “dietary blank” might conceivably be due to the presence of pyrimidines derived from the decomposition of thiamine in the diet. The final factor which made these studies necessary was the finding that during an acute thiamine deficiency the urinary pyramin excretion after a. few days of adjustment showed a progressive decrease to a level of 90 y per day. Stabilization of the pyramin excretion appeared to occur at that