Poly(ADP-ribose) biosynthesis and suicidal NAD+ depletion following carcinogen exposure of mammalian cells.

Hepatocytes were found to be remarkably resistant to suicidal NAD+ depletion due to consumption for chromatin-associated poly(ADP-ribose) biosynthesis, which normally follows infliction of DNA damage in mammalian cells. N-methyl-N'-nitro-N-nitrosoguanidine treatment, which depleted NAD+ levels of confluent fibroblasts to about 40% of controls, did not reduce hepatocellular NAD+ pools, although poly(ADP-ribose) concentrations were concomitantly elevated by 21-fold. This differential behavior, demonstrable also with other carcinogens, can be attributed to the different NAD+ biosynthetic capacities of these cells.