Effects of irradiation and inhibition of adenosine diphosphate ribosyl transferase in radiation sensitive and resistant mouse lymphoma (L5178Y) cells.

The effects of treatment with benzamide, an inhibitor of adenosine diphosphate (ADP) ribosyl transferase, were studied in two strains of L5178Y lymphoma cells of differential sensitivity to ionizing radiation. Continuous 2 mmol/l benzamide treatment enhanced the killing effect of roentgen irradiation in the sensitive cells, but not in the resistent cells. Three hours' treatment with 2 to 15 mmol/l benzamide sensitized irradiated cells of both strains to a similar extent. Rejoining of DNA breaks was delayed by 2 mmol/l benzamide in sensitive cells more than in resistant cells.