The effect of age on the variations of nuclease activities and their possible functions in rat liver

The measurement of the activities of different nucleases in homogenates and mitochondria of rat liver reveals that their activities are greatly increased if the determinations are carried out either in the presence of Triton X-100 or after freezing and thawing. The relative increases in the activities of these enzymes in mitochondria are considerably higher than those in homogenates if the activities are measured in the presence of Triton X-100. When the effect of age on the activities of these enzymes in the livers of rats is studied, it is found that their activities are much higher in the livers of very young and old rats. In young adult rat livers the activities of these enzymes are much less and during the period beginning from 10 weeks to 10 months, no significant changes in their activities could be observed. On the basis of the results obtained in the course of this investigation, it has been suggested that these enzymes might be in some unknown way involved in the synthesis of DNA and RNA in very young rats, while in old age they act exclusively as degradive enzymes.