TABLE II 



Amounts of Ribonucleic Acid Phosphorus (PNA-P) and Deoxyribonucleic 

 Acid Phosphorus (DNA-P) in Adult Rat Tissues" 



" Many authors express their results as amounts of PNA or DNA. For the purpose of this and the follow- 

 ing tables, their figures have been divided by 10, on the basis of the assumption that the P content of both 

 PNA and DNA is approximately 10%. 



'' 1 picogram (pg.) = 10~is gram. 



"^ There is a distinct lack of agreement among the results of various authors for kidney and spleen (Table 

 II). The explanation seems to lie in the different methods employed to measure PNA and DNA. When the 

 Schmidt and Thannhauser' method is used and PNA determined by measuring the P content of fraction 

 IV (Table I) the ratio PNA-P/DNA-P is over 2 for kidney and 1 for spleen (48, 56, 60, 61). When the Schneider 

 method (2) is employed, the PNA measured by orcinol and DNA by diphenylamine, the PNA-P/DNA-P 

 ratio is less than 1 for kidney (37, 55) and about 0.3 for spleen (37, 54). In kidney, the difference must lie in 

 the determination of PNA, as the DNA concentrations are much the same, whatever the method employed. 

 But, in spleen, the Schneider method gives a much higher figure for DNA and a lower value for PNA than 

 the Schmidt and Thannhauser method. The most likely errors in the former method arise from interference 

 by chromogenic substances in the orcinol and diphenylamine procedures, whereas in the latter procedure 

 the PNA-P as measured by the P content of fraction IV (Table I) is likely to give erroneously high 

 values, and, in certain cases, the DNA-P may be underestimated (see addendum, ref. 228 p. 45). 



" Skeletal muscles taken from the hind legs and shanks. 



