A model for compartmentation of de novo and salvage thymidine nucleotide pools in mammalian cells.

When [3H]thymidine is added to HeLa cells grown in thymidine-free medium it is incorporated into DNA almost immediately at full specific activity, blocking any further incorporation of de novo synthesized thymidine nucleotides. Apparently, de novo nucleotide pools [Baumunk, C.N. & Friedman, D.L. (1971) Cancer Res. 31, 1930--35] and salvage nucleotide pools are compartmentalized in HeLa cells. After one generation in the presence of thymidine, the cells begin utilizing nucleotides from both pools to about equal extent.