Role of dihydropyrimidine dehydrogenase in the uridine nucleotide metabolism in the rat liver

The activity of dihydropyrimidine dehydrogenase, which is the rate-limiting enzyme in the catabolism of pyrimidine, in livers of 5-day-old rats increased 48h after glucocorticoid injection. The increase in the activity of dihydropyrimidine dehydrogenase by glucocorticoid ad-ministration and by aging did not decrease the uridine, uracil and ΣUMP (the sum of acid-soluble uracil 5'-nucleotides) pool in liver. The increase of liver uracil by a uridine diet not increase dihydropyrimidine dehy-drogenase activity. The increase of liver uracil did not increase dihydro-pyrimidine dehydrogenase activity. However, dihydropyrimidine dehy-drogenase activity which increased after glucocorticoid treatment in-creased the pyrimidine-degradation rate in rat livers and hepatocytes. Pyrimidine catabolism pathway in liver may play an important role in degradation of dietary pyrimidines and pyrimidines which are adminis-tered in the form of medicines as 5-fluorouridine.