Delayed synthesis of uracil-degrading enzymes in regenerating rat liver

Abstract

• 1.

  1. The levels of the uracil-degrading enzymes have been determined in livers from young rats and from rats with different capacity to incorporate uracil into liver RNA. It was found that liver growth or increased ability of the liver to incorporate uracil into the nucleic acids was not necessarily associated with decreased levels of the uracil-degrading enzymes.

• 2.

  2. The rate of synthesis of dihydrouracil dehydrogenase (4,5 dihydrouracil: NADP oxidoreductase, EC 1.3.1.2) has been calculated from growth data and enzyme values from studies of regenerating rat liver, and it has been shown that the decrease which occurs in dihydrouracil dehydrogenase activity during liver regeneration can be adequately explained by assuming a 24-h delay of the synthesis of the enzyme after initiation of liver growth. It is concluded that a decrease in uracil-degrading activity is not involved in the initiation of liver growth.

• 3.

  3. Some factors which could possibly control the synthesis of dihydrouracil dehydrogenase in regenerating rat liver have been examined.