THE INCORPORATION OF NICOTINIC ACID AND OF NICOTINAMIDE INTO THE PYRIDINE NUCLEOTIDES OF ERYTHROCYTES AND RETICULOCYTES OF RABBITS IN VITRO*

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Abstract
Diphosphopyridine nucleotide (DPM) and triphosphopyridine nucleotide (TPN) were isolated from erythrocytes and reticulocytes of rabbits after incubation for 4 hours with glucose, glutamine, inorganic phosphate and nicotinic acid-7-C14 (NA) or nicotinamide-7-C14 (NAM). Incorporation of NAM greatly exceeded incorporation of NA. Incorporation of both NAM and NA into the DPN of reticulocytes was 4 to 5 times greater than incorporation into DPN of erythrocytes. Labeling of reticulocyte TPN was also much greater than that of erythrocyte TPN. The ability to incorporate NA and NAM into DPN and TPN appears to decline when rabbit reticulocytes mature to become erythrocytes. The mechanism that determines this decreased capacity remains to be defined.