Effects of nicotinamide on NAD and poly (ADP‐ribose) metabolism in DNA‐damaged human lymphocytes

Abstract
The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two‐fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the burst of poly(ADP‐ribose) synthesis caused by MNNG treat‐ment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP‐ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.