FORMATION OF DEOXYRIBONUCLEOSIDE 5'-MONOPHOSPHATES DEPENDENT ON DNA-SYNTHESIS IN NUCLEI ISOLATED FROM REGENERATING RAT-LIVER

Hydrolysis of deoxyribonucleoside 5''-triphosphate [dNTP], resulting in deoxyribonucleoside 5''-monophosphate [dNMP] formation dependent on DNA synthesis, was observed in nuclei isolated from regenerating rat liver. The intensity of the hydrolysis in nuclei varied at different times after partial hepatectomy, showing its maximum at 48 h. The rates of DNA synthesis altered corresponding to the intensities of hydrolysis. Proportionality between decrease in DNA synthesis and decrease in dNMP production was also observed in nuclei treated with various inhibitors of DNA synthesis. The formation of dNMP was detected with the 4 DNA substrates, indicating no involvement of specific dNTPase. Although regenerating nuclei contained a nonspecific dNTPase activity that can cause release of dNMP, this activity was independent of DNA synthesis and not inihibited by inhibitors of DNA synthesis. Regenerating liver nuclei may have 2 different activities for dNMP production; one is DNA synthesis-dependent, and the other is a non-specific dNTPase activity. The former activity was emphasized.