Studies on enzymes involved in nucleic acid metabolism in foetal, young and regenerating rat liver

Abstract

The activities of enzymes involved in nucleic acid metabolism in fetal, young and regenerating rat liver were compared with those in normal rat liver. Thymidine phosphorylase and uridine phosphorylase were less active in fetal and young liver than in adult liver. Thymidine-phosphorylase activity was also reduced in regenerating liver. Thymidine was incorporated into DNA in vitro more rapidly in the liver of fetal and young rats than in adult rats. Dihydro-orotase activity was maximal in the liver at birth when it was twice as active as in the adult. Total-body X-radiation (400 r), when given to rats 6 hr. after partial hepatectomy, delayed the decrease in thymine catabolism.