MURINE GLIAL-CELLS REGENERATE NAD, AFTER PEROXIDE-INDUCED DEPLETION, USING EITHER NICOTINIC-ACID, NICOTINAMIDE, OR QUINOLINIC ACID AS SUBSTRATES

The potential for regeneration of intracellular pyridine nucleotide le vels from different precursors, after peroxide-induced NAD depletion, in cultured glial cells was investigated, Cultured murine glial cells showed a decrease in intracellular NAD levels of >40% after treatment with H2O2 (100 mu M). Removal of the H2O2 followed by a 2-h incubation did not result in NAD recovery in the absence of precursors. However, NAD levels increased significantly in these cells after the following substrate additions, at minimum effective concentrations of 1 mM for quinolinic acid (QUIN), 500 mu M for nicotinamide, and 2 mu M for nico tinic acid. The regeneration of significant amounts of NAD from nicoti nic acid at doses 250 and 500 times lower than either nicotinamide or QUIN indicates a preferred route for NAD biosynthesis in glial cells i n vitro, probably via nicotinic acid phosphoribosylation.