DELAYED INCORPORATION OF TRITIATED THYMIDINE INTO DNA.

Delayed utilization of tritiated thymidine by regenerating mouse liver can be almost completely suppressed by a continuous infusion of nonradioactive thymidine. In addition, as shown earlier for lymphocytes, labeled granulocytes are a potential source of the tritium marker. These observations suggest that the delayed incorporation of label into DNA must be due to the transfer of labeled nucleoside, which may be derived either from the degradation of DNA or from a long-lived intracellular pool. In either case, the transferred material probably originates from all tissues that have a high rate of cell turnover.