Labeling DNA with stable isotopes: Economical and practical considerations

Labeling DNA with stable isotapes to measure cell proliferation can be a te chnique as effective as H-3-tymidine labeling without the limitations impos ed by using radiotapes. Here, we investigated the relative efficiency of fo ur nonradioactive precursors to DNA: [1-C-13]-glycine, [1,2-C-13(2)]-glycin e, [U-C-13]-glucose, and [U-C-13, N-15]-tymidine. The efficiency of incorpo ration for each of these labeled precursors in HEP G2 cells in culture has been studied. When considering the actual costs of in vivo experiments in w hich large doses of labeled material are needed, economical constraints may play an important role in defining a practical method. Therefore, the econ omics of this process were also considered. Using the enrichment per dollar for whichever nucleoside had the highest incorporation in a given experime nt, glycine is about five times more economical as a label than thymidine a nd eight times more economical than glucose in these cells.