Influence of inhibitors of poly(ADP-ribose)polymerase activity on X-ray and ultraviolet light induced killing and mutation in Chinese hamster V79 cells.

The effect of nicotinamide or benzamide, inhibitors of poly(ADP-ribose)polymerase activity, on X-ray and ultraviolet light induced killing of asynchronously dividing V79 Chinese hamster cells was to reduce the shoulder width of the survival curve; the rate of killing remaining unchanged and the yield of 8-azaguanine resistant mutants also remaining unaffected. However, when density inhibited cells were irradiated with X-rays or u.v. light, holding at this density allowed potentially lethal damage recovery (PLDR) to occur, enhancing survival. Inhibitors of poly(ADP-ribose)polymerase suppressed PLDR and also increased the yield of mutants. Thus the role of poly(ADP-ribose) in X-ray or u.v. induced killing and mutation was dependent on the condition of growth.