776 ADVENTURES IN EADIOISOTOPE RESEARCH 



30 per cent of the phosphatides present in liver shoes in the course 

 of 6 hr.(^) The value for the specific activity of the free phosphate extracted 

 from tissue sections at the end of the experiment by thorough washing 

 is, for the reasons mentioned above, found to be possibly too low. 



FORMATION OF NUCLEIC ACID CONTAINING 32p 



We have always performed simultaneously two strictly analogous 

 experiments. One half of the mixture of sarcoma sections was used for 

 one experiment and the remaining half for the second, but in one of 

 these experiments a substance whose inhibiting effect on the formation 

 of nucleic acid could be studied was added to the bicarbonate-Ringer's 

 solution or to the heparinized blood or plasma. 



Formation of Nucleic Acid with and without Addition of KCN 



In experiment (a) 8.7 gm and in experiment (b) 10.0 gm of tissue sections 

 were placed in 300 cm^ Erlenmeyer flasks containing 30 cm^ of bicarbo- 

 nate-Ringer's solution (Krebs-Henseleit) at pH 7.4. In experiment (b) 

 5.7 mgm KCN was also added (pH of the solution also 7.4). After shaking 

 for 15 min at 37.5° C we added to each mixture 0.4 cm^ of physiological 

 saline containing active sodium phosphate and then bubbled a gas 

 mixture of 95% Og and 5% COg through the vessels. After 2 hr had 

 passed oxygen and COg were again bubbled through. The time of experi- 

 ment amounted to 4 hr. At the end of the experiment the sections were 

 washed ten times with inactive bicarbonate-Ringer's solution or physiolo- 

 gical saline solution and this was followed by extraction and purification 

 of the nucleic acid: 



sample I (without KCN) yielded 9.40 mgm of purified nucleic acid; 

 sample II (with KCN) yielded 16.5 mgm. The activity of sample I was 

 84 and of sample II, 0.7. 



^^^ The facts described make it more difficult to decide the problem, of whether 

 or not, for example, the activity of the creatine phosphoric acid P becomes equal 

 to that of the free intracellular P in the course of a relatively short time. Decom- 

 position of a part of the creatine phosphoric acid and other compounds, which 

 are less active than the free intracellular P, lowers the specific activity of the 

 intracellular P and thus narrows the difference between the specific activities 

 of the creatine phosphoric acid P and the true intracellular free P until it more 

 or less vanishes. The results which have been obtained by comparing the specific 

 activities of various other organic P fractions, on the contrary, are fully guaran- 

 teed: e. g., we have full information on the relative rates of renewal of the three 

 P atoms in adenosine phosphoric acid (Ftxbchgott and Shorr, J. Biol. Chem. 

 151, 65 (1943), E. V. Block and J. L. Bollman, J. Biol. Chem. 152. 371 (1944). 



