The effect of RNA supplementation of rat diets on the composition of body fluids.

1. In a number of separate experiments, yeast RNA, mixtures of its constituent nucleosides, its constituent bases and ribose were administered orally to rats. In each instance, the resultant changes in the composition of body fluids were monitored using sensitive methods. 2. Ingestion of RNA (100 g/kg diet) caused detectable increases in intestinal ribose, inorganic phosphate, uridine, pseudouridine, uracil, inosine, uric acid and probably other purine bases. Their accumulation did not detectably affect the rate of passage of food along the digestive tract, even though some nucleosides are known to affect gut motility. 3. Although plasma levels of uric acid and uridine were higher when RNA was administered in the diet, these changes were very slight compared with those in plasma uracil, which in some experiments were increased more than 20-fold compared with control levels (300 mumol/l). Analysis of erythrocytes indicated that the internal environment of at least some cells of the body are similarly altered. 4. Analyses indicated that all dietary RNA-phosphate passed into the urine from the gut but most of the RNA-ribose was probably metabolized. Uracil and uric acid levels in the urine reflected plasma composition. 5. The effect of orally administered mixed nucleosides on blood and urine composition was similar to that of RNA, but the response to an equivalent mixture of free bases differed in several respects; cytosine, adenine and hypoxanthine appeared in urine only under these circumstances.