Action of hydroxyurea on the nucleic acid metabolism and viability of HeLa cells.

of 16 hr produced a loss of cell viability accompanied by an inhibition of DNA synthesis. Continued synthesis of RNA and protein suggests an unbalanced growth similar to that previously observed with 5-fluorodeoxyuridine, excess thymidine, and 1-/8D-arabinofuranosylcytosine. A threefold increase in thymidine kinase activity was observed as a result of unbalanced growth following the exposure of cells to hydroxyurea. When cells were exposed to 10~2Mhydroxyurea for short exposure times, however,