DNA repair synthesis in cultured mammalian and fish cells following exposure to chemical mutagens.

Unscheduled DNA repair synthesis (UDS) was measured autoradiographically in HF, CHO, RTG, RTO, CH and FHM cells given a 3-h exposure to MNNG, 4NQO, NA2AAF and AFB1. All the chemicals produced a dose-response, the magnitude of which varied with the particular chemical and cell line. HF produced the greatest response, CHO less and the fish cell lines the least. The response of all fish cell lines was approximately equal for a particular chemical. A number of factors were investigated to account for the comparative differences in UDS response. The time course of repair in HF, CHO and RTG following a 3-h exposure to MNNG or 4NQO was the same. As S-phase nuclei were observed in control slides and the amount of repair following UV exposure varies HF greater than CHO greater than RTG, neither 3HTdR nor mutagen uptake is limiting. The observed results are discussed.