Reactivation of NAD(H) biosynthetic pathway by exogenous NAD+ in Nil cells severely depleted of NAD(H).
The culture of Nil hamster fibroblasts in MEM lacking nicotinamide (NAm-MEM) leads to: (1) the rapid loss of intracellular total nicotinamide adenine dinucleotide (NAD(H)) content in these cells from a level of 150-200 pmoles/10(5) cells to less than 20 pmoles/10(5) cells; (2) the cessation of cell division and inhibition of DNA synthesis; and (3) a reduction of glucose consumption and lactic acid production. In most situations, following nicotinamide starvation, the restoration of intracellular NAD(H) follows rapidly the readdition of NAD+ (oxidized), nicotinamide mononucleotide (NMN), nicotinamide, or nicotinic acid. Resumption of cell division occurs after only a lag of about 24 hours. Nil cells subcultured for three consecutive times in the absence of nicotinamide (3(0) NAm- cells) exhibit different behavior. These severely starved cells are incapable of quickly restoring their intracellular NAD(H) content to normal levels when provided with any pyridine ring compound except NAD+. One-hour exposure of such cells to NAD+ allows utilization of nicotinamide to rapidly restore intracellular NAD(H). This short incubation with NAD+ does not result in any significant restoration of intracellular NAD(H) or lead to the accumulation of an intracellular pool of some precursor. This function of NAD+ as a stimulatory signal to the NAD(H)-biosynthetic pathway in severely starved Nil cells is a previously unreported role of NAD+, and does not require protein synthesis.
D000818:Animals; D002455:Cell Division; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000032:analysis; D005347:Fibroblasts; D005947:Glucose / Q000378:metabolism; D007399:Interphase; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D009243:NAD / Q000096:biosynthesis* / Q000494:pharmacology; D009525:Niacin / Q000378:metabolism; D009536:Niacinamide / Q000378:metabolism / Q000494:pharmacology; D009537:Nicotinamide Mononucleotide / Q000378:metabolism; D014176:Protein Biosynthesis
D007773:Lactates; D009243:NAD; D009537:Nicotinamide Mononucleotide; D009536:Niacinamide; D009525:Niacin; D019344:Lactic Acid; D004247:DNA; D005947:Glucose