THE METABOLISM OF EXOGENOUS RIBONUCLEIC ACIDS INJECTED INTO MICE

Abstract

The fate of ribonucleic acid (RNA) administered intravenously was investigated in mice and rats, using yeast RNA uniformly labeled with C14 Much of the administered radioactivity was found in the CO2 exhaled within 5 hours, the rest being distributed mostly between the free nucleotides and carbohydrates of the 9 tissues tested. Brain showed consistently low values in all chemical fractions. Administration of large amounts of RNA over a period of 5 days caused an increase in the incorporation of radioactivity into the nucleic acids of liver and kidney and into the amino acid pool of the body. A slight increase in protein synthesis in the brain was also noted. From results obtained by studying the rate of appearance of the radioactivity in the CO2 after injections of labeled RNA, ribose, orotic acid, and RNA mixed with unlabeled ribose, it was concluded that most of the exogenous RNA, when injected, is rapidly degraded before re-utilization of some of its components.