Rate of Renewal of Ribo‐ and Desoxyribo Nucleic Acids

Summary. Labelled sodium phosphate is administered to rats and after the lapse of 2 hours the specific activity of the ribo‐nucleic acid phosphorus and that of the desoxyribo‐nucleic acid phosphorus determined. In the liver the specific activity of the ribo‐nucleic acid P is found to be 33 times larger than the specific activity of the desoxyribo‐nucleic acid P. In the course of 2 hours about 0.1 and 3.3 per cent respectively of these compounds were found to be renewed. In the intestine and in the spleen in which the specific activity of the desoxyribo‐nucleic acid is found to be about 20 times larger than the corresponding value in the liver, the specific activity of the ribo‐nucleic acid phosphorus is only 2 to 3 times larger than the corresponding value of the desoxyribo‐nucleic acid phosphorus. The ribo‐and the desoxyribo‐nucleic acid phosphorus extracted from the total rat have a very similar specific activity to the corresponding phosphorus extracted from the intestine. In the total rat the difference in the rate of renewal of the two types of nucleic acid is not very pronounced. In a rat weighing 200 g approximately about 2 mg desoxyribo‐phosphorus and 3 mg ribo‐nucleic acid phosphorus are turned over in the course of 2 hours.