678 



ADVENTURES IN RADIOISOTOPE RESEARCH 



tance of these organs in protein metabolism. The incorporation of labehed 

 sulfur into protein sulfur is found to be higher in the intestine than in 

 any other organ (Tarver and Schmidt, 1942) and the i^N content of 

 the proteins isolated from the intestinal wall of the rat after adminis- 

 tration of isotopic 1( — )-leucine is larger than the corresponding value 

 for any other organ investigated. Somewhat smaller values for the i^N 

 content of the proteins isolated from the spleen were found, and still 

 smaller values for the ^^N of the proteins isolated from the Hver (Schoen- 

 HEiMER, Ratner and Rittenberg, 1939). The rate of formation of 

 ribose nucleic acid in these three organs diminishes in the same sequence. 



If we want to state, not as above the percentage, but the amount of 

 nucleic acid formed during the experiment, we must know the nucleic 

 acid content of the organs of the rat and of the total rat. 



Some preliminary figures for the total nucleotide P of the liver, spleen, 

 intestine and total rat and also some preliminary figures for the share 

 of polydesose and polyribo nucleotides in the total nucleotides is seen 

 in Table 3. The method applied in obtaining these figures and more 

 accurate data will be shortly published by one of the authors. 



Table 3. — Polydesose Nucleotide Phosphorus and Polyeibo Nucleotide 

 Phosphorus Content of Some Organs and of the Total Rat 



Approximate 

 share of poly- 

 desose nucleotides 

 in the total 

 nucleotides % 



gm nucleotide 



P per 100 gm 



dry weight 



Total rat 

 Liver . . , 

 Spleen . . 

 Intestine 



45—50 

 35 

 75 

 57 



gm polydesose 

 nucleotide 



P per 100 gm 

 dry weight 



0.232 

 0.350 

 0.643 

 0.669 



0.11 

 0.12 



0.48 

 0.38 



gm polyribo- 

 nucleotide 

 P per 100 gm 

 dry weight 



0.12 

 0.23 

 0.16 

 0.29 



Assuming the percentage formation of the polydesose nucleic acid of 

 the total rat in the course of 2 hours to be 4 (cf. p. 676) and the fresh 

 weight of the rat to amount to five times its dry weight, in a 200 gm rat 

 in the course of 2 hours about 2 mgm polydesose nucletoide P will be 

 incorporated. The corresponding figure for the polyribo nucletoide P 

 works out to be 3. In the total rat the rate of formation of the 2 types 

 of polynucleotides does thus not differ very appreciably. 



A very different result is obtained when comparing the amount of 

 polydesose and polyribo nucleotide phosphorus incorporates in the liver. 

 The figures work out, assuming the liver to weigh 6 gm,to be 0.0017 mgm 

 and 0.094 mgm respectively. Fifty-five times more polydesose nucleotide 

 than ribonucleotide is thus formed in the liver during the same time. 



