RNA-POLYMERASE, DNA-POLYMERASE, DNA-METHYLTRANSFERASE AND SPHINGOMYELINASE ACTIVITIES IN LIVER NUCLEI OF RATS OF DIFFERENT AGE

It has been established that activities of RNA-polymerase, DNA-polymer ase, DNA-methyltransferase, and sphingomyelinase in the liver nuclei i solated from newborn (2-day-old) rats are by 18, 25, 27, and 610%, res pectively, higher than those in mature (6-month-old) rats. It has been also shown that the number of single-stranded stretches in rat liver nuclear DNA increases with age: it is about 2-fold higher in mature ra ts than in newborn rats. Thus, the postnatal period of ontogenesis is accompanied by both significant changes in DNA structure and decrease in activities of enzymes serving for the most important genetic proces ses in cells of animals.