The time course of DNA repair following methyl nitro-nitrosoguanidine (MNNG) treatment of p388f lymphoma cells in culture. II. DNA repair synthesis and its correlation with strand breakage.

Repair synthesis has been followed in P388F cell DNA following treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) using 5-iodo-deoxyuridine (IUdR) and [3H] thymidine combination. A pattern of repair synthesis was obtained, similar in its timing to the initial and medial stages of single-strand break formation and rejoining within the first 24 h after treatment. A higher base insertion frequency in relation to single-strand breaks occurs during the medial stage of repair. However, a fundamental problem with the use of iododeoxyuridine and [3H] thymidine ([3H] TdR) as a suitable measure of repair synthesis was encountered and a potential source of error in such experiments was observed.