RENEWAL OF DESOXYRIBO NUCLEIC ACIDS 



675 



of columns 2 and 3 of Table 1 should therefore be multiplied by 1.05 

 in the case of the liver, for example, to obtain a correct value for the 

 amount of the rate of renewal of the desoxyribo nucleic acid present 

 in the liver. In the figures of Table 1 we have not introduced this cor- 

 rection, as we are mainly interested in the relative rate of renewal of 

 the desoxyribo and ribo nucleic acids. 



Table 1 contains the results of an experiment in which three rats in 

 nitrogen-equilibrium weighing 252, 182 and 215 gm were injected sub- 

 <'utancously with respectively 7.5, 6.6 and 5.6 microcuries of ^^p per 

 100 gm body weight. 



After 2 hours the animals were killed and the organs prepared according 

 to a method which will soon be published by one of the authors. 



Table 1. — Ratio of the Rate of formation of the Ribo 



Nucleic Acid and Desoxyribo Nucleic Acid in the organs 



OF the Rat in the Course of 2 Hours 



As recorded in Table 1, the rate of renewal of ribo nucleic acid in 

 the liver is as much as 33 times larger than the rate of renewal of deso- 

 xyribo nucleic acid. In spite of the finding that ribo nucleic acid is 

 renewed at an even larger rate in the spleen and the intestinal mucosa 

 than in the liver, the ratio of the rate of renewal of ribo- and desoxyribo- 

 nucleic acids in these organs is only 3 and 2, respectively. This low 

 ratio is due to the comparatively high rate of formation of desoxyribo 

 nucleic acid in these organs. From the above figures it follows that the 

 rate of renewal of both types of nucleic acid is highest in the intestinal 

 mucosa and in the spleen. 



The specific activity of both the desoxyribo and the ribo nucleic acid 

 P extracted from the rat liver was determined by Brues, Tracy and 

 CoHN (1944) in experiments lasting 3 to 8 days. In these experiments 

 the ribo nucleic acid P was found to be only 5 to 6 times as active as 

 the desoxyribose nucleic acid P. The discrepancy between these figures 

 and those obtained by us may be due, at least mainly, to the much 

 longer duration of the last mentioned experiments. 



43^ 



