Nicotinamide Adenine Dinucleotide Synthesis in Ascites Cells in Vitro.

Previous studies in our laboratory (1) have shown that intact ascites cells incorporate nicotinamide-14C into both nicotinamide adenine dinucleotide and nicotinic acid adenine dinucleotide. It was also shown that the specific activity of the nicotinamide adenine dinucleotide increased with increasing concentrations of nicotinamide-14C. High levels of nicotinic acid-r4C, on the other hand, did not increase but appeared to inhibit the incorporation of nicotinic acid-r4C into nicotinamide adenine dinucleotide. It was not possible, at that time, to determine what fraction of the nicotinamide-14C incorporated into the cellular nicotinamide adenine dinucleotide was contributed by the nicotinamide adenine dinucleotide glycohydrolasel activity of the cell and what fraction was the result of synthesis de novo of the dinucleotide. This question, together with the general ambiguity concerning nicotinamide adenine dinucleotide synthesis from nicotinamide, led to the present study.