Further insight into NAD synthesis in human erythrocytes: significance and relevance.

The cellular levels of NAD and its rate of synthesis from nicotinic acid (NA) were found to decrease from reticulocyte-rich fractions to mature erythrocytes separated on a density gradient. Decreased activity of NA-phosphoribosyltransferase in crude lysates was also observed from young to mature cells, while the uptake of extracellular NA did not show any difference. Impaired NAD synthesis, more likely than progressive breakdown, is suggested to cause NAD decrease during erythrocyte maturation.