HYDROLYSIS — ESTIMATION OF BASES IN PNA 209 



The results for the extracted ribonucleic acid preparations from several 

 types of tissues and animal species show a wide variation in composition 

 depending on the methods of extraction and analysis that are used.-^' ^^^ "• " 

 It is also clear that the composition of the ribonucleic acid fractions ex- 

 tracted from isolated mitochondria varies depending on the method used 

 for extraction.*'- " Thus, apparently more than one chemical species of 

 ribonucleic acid may be present in this tj^pe of cytoplasmic component. 

 The analytical results for the acid and alcohol-ether extracted mitochondria, 

 microsomes, and nonsedimentable ribonucleic acid fractions from mouse 

 liver found by the analytical procedure outlined above are summarized in 

 Table IV. (Unpublished experiments of the author with J. L. Fairley, H. 

 L. Seagran, R. S. Waritz, and M. D. Johnson.) The reproducibility of the 

 method is shown from the values of the standard deviations of the means 

 in a series of six separate analyses of a pool of normal mouse liver pow- 

 der. Because the variation between pools of mitochondria, microsomes, 

 or nonsedimentable ribonucleic acid fractions is larger than that in a single 

 pool, the results strongly suggest that variations occur in the ribonucleic 

 acid of the different cytoplasmic fractions even in animals under comparable 

 conditions. Under fasting conditions or in mice carrying the- Ehrlich ascites 

 tumor variations beyond those normally found also apparently occur. 



Of considerable interest in the above-mentioned studies is the relative 

 amount of ribonucleic acid in mitochondria and microsomes as judged by 

 the molar ratios of total purine and purine and pyrimidine base to phos- 

 phorus present. If the assumption is made that the base to phosphorus 

 ratio in ribonucleic acid is one, then it can be concluded that significant 

 amounts of trichloroacetic acid-insoluble phosphoiTis compounds other than 

 nucleic acid are present in such cytoplasmic fractions and to a greater ex- 

 tent in mitochondria than in microsomes. In view of statements in the 

 literature" • '''^ that rat liver mitochondria may contain only small amounts 

 of ribonucleic acid, it may be pointed out that the amounts of purine 

 and pyrimidine bases found in trichloroacetic acid and alcohol-ether ex- 

 tracted mitochondria account for from 60 to 80% of the phosphorus 

 present. 



In several instances isolated cell nuclei have also been analyzed for their 

 ribonucleic acid components. The results"' "• ''^ are apparently highly vari- 

 able depending on the method of preparation of the nuclei. 



'< V. R. Potter, R. O. Rechnagel, and R. B. Hurlbert, Federation Proc. 10, 646 (1951) . 

 '* W. M. Mc Indoe and J. N. Davidson, Brit. J. Cancer 6, 200 (1952). 



