THE INCORPORATION OF TRITIUM FROM THYMIDINE INTO PROTEINS OF THE MOUSE

摘要

Tritium from methyl—3 H-Thymidine was found to be incorporated into proteins in mice. This incorporation in the mouse as a whole represented between 1 and 10% of the injected tritium. Tritiated water was not responsible for the labeling. Transmethylation reactions were proposed as a means whereby certain amino acids might have acquired the tritium from Thymidine at some stage of its catabolysis. The initial (2-hour) ratios of DNA to protein tritium activities per mg wet tissue ranged from 5 in two tissues of low DNA synthetic activity (pancreas, liver) to 35-40 in two tissues of high DNA synthetic activity (spleen, small intestine). Labeled nuclear protein was coincident with labeled DNA in nuclei, where it constituted less than 2.5% of the total tritium. The significance of the findings was discussed.