Autoradiographic studies of pyridine nucleotide metabolism in human culture cells

✍ Scribed by Martin Rechsteiner; Keith Lund; David Hillyard; Baldomero Olivera

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 892 KB
• Volume: 83
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040830309

✦ Synopsis

Abstract

More than 80% of the intracellular pyridine metabolite pool of human culture cells is trapped by OsO~4~ fixation. The fixed pyridine metabolites fully exchange with nicotinamide and nicotinic acid but not with nicotinamide adenine dinucleotide. Yet, chromatography of the exchanged compounds reveals that NAD and NADP constitute more than 95%. of the fixed material. Although the mechanism of OsO~4~ fixation is not fully understood, such fixation has permitted the autoradiographic detection of intracellular pyridine metabolites. Cells of the human cell line, D98/AH2, synthesize pyridine nucleotides during all phases of the cell cycle at rates which do not vary by more than six‐fold. There is no difference in the apparent concentration of pyridine metabolites between nucleus and cytoplasm after ten minute or three day pulses with ^3^H‐nicotinic acid. The ^3^H‐labeled pyridine ring is lost from D98/AH2 cells upon transfer to unlabeled medium. In general, the rate of loss is uniform among cells in the population. However, in a small proportion of cells there is little or no loss. Non‐dividing cells lose the pyridine ring at approximately the same rate as dividing cells, yet the intracellular concentration of pyridine metabolites is 50% greater in non‐dividing cells.