Deoxyribonucleotide Pools during Liver Regeneration

The intracellular pools of deoxyribonucleotides were analyzed during liver regeneration in rats. In normal liver the content of dATP, dCTP, dGTP and dTTP was found to be 0.3, 1.3, 0.3 and 0.4 pmol per μg DNA, respectively. When the liver tissue started to proliferate the pools of the individual deoxyribonucleoside triphosphates increased and reached maxima at 24–27 h after partial hepatectomy. This increase in the levels of deoxyribonucleotides coincided in time with the peak of DNA synthesis as measured by the incorporation of labeled thymidine. A burst of mitotic activity was observed at 32 h. During liver regeneration ribonucleotide reductase is induced; the activity of this enzyme was found to be maximal at 50 h after partial hepatectomy, i.e. when the deoxyribonucleoside triphosphate pools as well as the rate of DNA synthesis had declined, indicating a feed‐back control of the enzyme.