Growth Inhibition of Chick-Embryo Cells by Some 5-Fluorinated Pyrimidiness: Effect on Rous Sarcoma Virus Infection

Abstract

Except for a tenfold difference with 5-fluorouridine, the toxicities of several fluorinated pyrimidines and their corresponding nucleosides for secondary cultures of chick-embryo fibroblasts were similar to those previously reported for human tumor and other mammalian cell lines. Reversal patterns with pyrimidine metabolites were similar for 5-fluoro-2′-deoxyuridine and 5-fluoro-2′-deoxycytidine, but different with 5-fluorouracil and 5-fluorouridine. Reversal of 5-fluoro-2′-deoxyuridine inhibition by deoxyuridine appeared to be of the competitive type, while the reversal by thymidine suggested noncompetitive reversal. An approximately 15-hour period during which complete growth inhibition could be reversed by transfer to thymidine-supplemented medium was noted. Incubation of chick-embryo fibroblasts in 5-fluoro-2′-deoxyuridine for 18 hours before or after exposure to Rous virus had no significant effect on their capacity to be transformed to sarcoma cells, as measured by the appearance of foci of transformed cells in the in vitro assay procedure.