RIBOSENUCLEIC ACID IN THE JENSEN-SARCOiL\ OF THE RAT 685 



and Thanhauser has the advantage that it permits a quantitative 

 or almost quantitative isolation of desoxyribosenucleic acid and can 

 thus be carried out even if only small tissue samples are available. 



The Average Value of the Specific Activity of the Inorganic P in the 

 Sarcoma during the Experiment 



The specific activity of the cellular inorganic P of the sarcoma de- 

 pends on the rate (a) at which the labelled phosphate reaches the surface 

 of the cells, (b) at which it penetrates into the cells of the tissue, (c) at 

 which it is incorporated into organic P compounds in the cells (the 

 incorporation of the inorganic ^'^P into organic compounds goes hand 

 in hand w ith the corresponding formation of inactive phosphate by the 

 degradation of the inactive organic compounds present in the cells of 

 the tissue). The magnitudes of these rates varies between the sarcomata. 



When comparing the specific activities of the inorganic P fractions 

 extracted from fresh and necrotic sarcoma 2 hours after the adminis- 

 tration of ^^P tissue, we found previously^^) that the values determined 

 in the fraction of necrotic sarcoma were roughly only half the magnitude 

 of those computed in the fraction extracted from fresh sarcoma. Also, 

 the values obtained for the specific activity of inorganic P extracted 

 from different parts of the fresh sarcoma tissue varied widely^^\ In the 

 experiments here reported, each rat was first inoculated with Jensen- 

 sarcoma and 15 days later 0.1 ml physiological sodium chloride solution, 

 containing a negligible amount of phosphorus of about ^4 microcurie 

 activity was administered to each rat. The 12 rats were sacrifced Yo, ^, 

 iVo and 2 hours respectively after the administration of ^'^P. The ratio 

 between the end values and the average value of the specific activities 

 of the tissue inorganic P was found to vary between 1.17 and 1.57. 

 In view of these variations it would be advisable to determine in each 

 case the average specific activity of the sarcoma inorganic P. This 

 presents great difficulty as such determinations would necessitate to 

 secure samples from the same sarcoma at different dates. We determine 

 therefore usually only the end value of the specific activity of the sar- 

 coma inorganic P and assume this to be 1.3 times the average value. 

 We arrive at the last mentioned figure by taking the average of the 

 results obtained in experiments as described above. Correspondingly, we 

 have to multiply the values of the "percentage new-formation", obtained 

 l)y comparing the end values of the specific activity of the nucleic acid P 

 with the specific activity of the end- value of the inorganic P, by 1.3 

 to arrive at the correct value of the percentage renewal of the sarcoma 

 nucleic acids in experiments lasting 2 hours (cf. Table 3 in which the 



^2>n. EuLER and and G. Hevesy, Ark. Kemi A 17, No. 30 (1944). 



