Induction of DNA repair synthesis by ultraviolet radiation and methylmethanesulphonate in cultured mouse lymphocytes.

The induction of DNA repair synthesis by UV-radiation and methyl-methanesulphonate (MMS) was studied in mouse lymphocytes and leukemic cells by means of autoradiography and scintillation counting, after labelling in vitro with tritiated thymidine ([3H]dThd). Repair stimulation was detected by both procedures in LSTRA and YC8 leukemic cell lines as well as in primary fibroblasts of BALB/c and BALB/Mo mice. No stimulation was observed in primary cultures of lymphocytes from the spleen, thymus and lymph-nodes of the same mice. In primary lymphocytes neither stimulation with concanavalin A (Con A) nor pre-incubation with 5-bromodeoxyuridine (BUdR) were effective in making evident DNA repair. The data put into question the reliability of the repair test for the prediction of carcinogenic potential of chemicals.