NICLEIC ACID IN THE CIRCULATION 767 



under enzymic action which is partly carried into the circulation and 

 partly enzymically incorporated into the organic P compounds present 

 in the cytoplasma and in the nuclei of the liver. The splitting-oil' results- 

 in a high labelled free phosphate and labile organic phosphate level in 

 the liver tissue. The regenerating liver tissue is very effective in taking 

 up chromatin from the circulation as follows from Marshak and Wal- 

 ker's investigation. They found the liver to take up 26.3 per cent of the 

 ^^P administered as chromatin, while only 4.4 per cent of the -^^ p admi- 

 nistered as sodium phosphate was taken up. The main phosphorus com- 

 jjound of the chromatin is desoxy ribonucleic acid. The phosphorus of 

 the nucleic acid present in the chromatin taken up by the liver can 

 therefore be expected to show a similar behaviour as the phosphorus of 

 the nucleic acid taken up by the liver, the fate of which is described in 

 this note. In both cases the bulk of the labelled phosphate taken up by 

 the liver is turned into free and acid-soluble organic phosphate, and a 

 part of which is then incorporated into the nuclei. 



Splitting- off of the Phosphate Group of Nucleic Acid by the Action 



of Liver SHces 



Liver slices incubated in bicarbonate Ringer solution were found to 

 be very effective in splitting off phosphate from desoxyribonucleic acid. 



3.36 gni resp. 3.52 gm liver slices of rats weighing 120 gm were incu- 

 l)ated in 9.8 ml phosphate-free bicarbonate ringer solution (pH = 7.8) 

 to which 18.6 mgm labelled desoxyribonucleic acid were added. Oxygen 

 containing 5 per cent COg was led through the Erlenmeyer flask, 

 containing the slices, which was gently shaken for 4 hours at 37°. The 

 slices were then separated by centrifugation. 



In the centrifugate 50 mgm non-active desoxyribonucleic acid were 

 dissolved, to facilitate the recovery of the active nucleic acid present 

 in the solution. The nucleic acid was then precipitated by hydrochloric 

 acid dissolved in metanol. After wet ashing and addition of 44 mgm of 

 non-active sodiumphosphate, the phosphorus was precipitated as mag- 

 nesiumammoniumphosphate. 



From the filtrate, after evaporating the metanol and addition of 80 

 mgm non-active sodiumphosphate, the free phosphate content was 

 recovered as magnesiumammoniumphosphate. 



The slices were washed with physiological sodiumchloride solution 

 4 times, the first washing liquid being added to the centrifugate prior 

 to the precipitation of the nucleic acid. A half of the slices was utilized 

 for the determination of the total ^^p content, the other half to the 

 determination of the acid-soluble ^^p content. The first named fraction 

 was extracted with 5 ml 10 per cent cold trichloracetic acid. The ^^P 

 content of the different fractions is seen in Table 7. 



