Increase of amidophosphoribosyltransferase activity and phosphoribosylpyrophosphate concentration as the basis for increased de novo purine biosynthesis in the regenerating rat liver.

The labeling of hepatic purines with [14C]glycine increased in the regenerating rat liver 12 hours after a 70% hepatectomy and it reached the 2.4 folds higher peak 12 hours after the surgical operation in comparison to sham-operated control. These observations suggest that the rate of de novo biosynthesis increases in the regenerating rat liver to supply purine ribonucleotides to the cells. In the regenerating rat liver the activity of amidophosphoribosyltransferase (ATase) significantly increased and reached the 1.8 folds higher peak than control 18 hours after surgery. Hepatic 5-phosphoribosyl 1-pyrophosphate (PRPP) concentration significantly increased and reached the 3.0 folds higher peak 12 hours after surgery. Although the mean hepatic concentration of ATP and GTP showed a 13 and 15% decrease respectively in the regenerating rat liver 12 hours after surgery, they were counterbalanced by the increased concentrations of AMP and GMP by 13 and 44% respectively. These results suggest that the increased rate of de novo purine biosynthesis in the regenerating rat liver is mediated by the increased enzymatic activity of ATase and by the increased concentration of PRPP.