The decreased rate of leucine incorporation into leucyl-tRNA by the pH 5 enzyme fraction from vitamin A-deficient rat intestinal mucosa was investigated. When tRNA from either normal or vitamin A-deficient rat intestinal mucosa was added to the vitamin A-deficient pH 5 enzyme fraction, the yield of leucyl-tRNA rose to normal levels. Freon column chromatography of iso-accepting leucyl-tRNAs and threonyl-tRNAs failed to show any qualitative difference between normal and vitamin A-deficient iso-accepting species. Hence, a decrease in the amount of tRNA available for charging is responsible for the decrease in charging activity of the pH 5 enzyme fraction from vitamin A-deficient rat intestinal mucosa. RNA synthesis in the intestinal mucosa of normal and vitamin A-deficient rats was studied after intraperitoneal injection of either 14C-6-orotic acid or 3H-G-uridine. In three experiments the amount of label incorporated into all RNA fractions was 30-45% higher in the vitamin A-normal than the vitamin A-deficient rats. Measurements of uridine, UMP, and UDP pool sizes and their specific radioactivities 1 hr after injection of the label revealed that the difference in RNA synthesis between normal and vitamin A-deficient rat intestinal mucosa represented a true difference in the incorporation of the label into RNA and not a dilution effect on the label in deficient rats.
ASJC Scopus subject areas
- Molecular Biology