Originally published in Acta Physiol. Scand. 11, 335 (194G). 



68. RATE OF RENEWAL OF RIBO- AND DESOXYRIBO 



NUCLEIC ACIDS 



E. Hammaesten and G. Hevesy 



From the Institute for Research in Organic Chemistry and the Chemistry 

 Laboratories of the Karolinska Institute, Stockhokn 



Enzymic processes coupled with phosphorylation often take place at a 

 remarkedly rapid rate. A large percentage of the molecules of many 

 of the acid-soluble phosphorus compounds and, to a minor extent, also 

 those of phosphatides present in the liver and some other organs are 

 renewed within a short time. This is demonstrated by the observation 

 that shortly after the administration of ^^P these molecules are found 

 to contain labelled phosphate. 



That the presence of ^^P in the molecules of organic phosphorus 

 compounds indicates an enzymic synthesis of such molecules is most 

 strikingly demonstrated by a recent experiment of Chaikoff and his 

 associates (1942). These authors have shown that labelled phosphatides 

 are formed when surviving liver slices are shaken with bicarbonate 

 Ringer solution containing labelled phosphate, that this formation is, 

 however, impaired in the absence of oxygen, and homogenized liver 

 tissue completely loses its ability to incorporate ^^P into the phosphatide 

 molecule. A non-enzymic process could hardly be dependent on the 

 intactness of the tissue cells. 



In contradistinction to the above mentioned compounds, as found in 

 previous (Hevesy and Ottesen, 1943 ; Ahlstrom, Euler and Hevesy, 

 1944 ; Brues, Tracy and CoHisr, 1944) and in the present investi- 

 gations, desoxyribo nucleic acid molecules present in the liver are at 

 a very slow rate only. This result falls in line with the view that deso- 

 xyribo nucleic acid is present in the nuclei of the cells and is involved 

 in the process of cell division. As the mitotic process in the liver of a 

 fully grown rat takes place at a very slow rate only, the low rate of 

 formation of desoxyribo nucleic acid in the fully grown liver is in 

 no way surprising, neither is the much higher rate of formation 

 observed in the liver of the only few days old rat. The rate of forma- 

 tion on new desoxyribo nucleic acid molecules present in the liver 

 of 3 to 4 days old rats was found to be about 20 times that of the 

 corresponding figure in outgrown rats (Ahlstrom, Euler and Hevesy, 

 1944). 



43 Hevesy 



