REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE-SELECTIVE STIMULATION OF INOSITOL 1,4,5-TRISPHOSPHATE RECEPTORS MEDIATES HYPOXIC MOBILIZATION OF CALCIUM

To evaluate the relationship of inositol 1,4,5-trisphosphate (IP3) rec eptor-mediated signal transduction and cellular energy dynamics, we ha ve characterized effects of nucleotides on IP3 receptor (IP(3)R)-media ted calcium (Ca2+) flux in purified IP3 receptors reconstituted in lip id vesicles (IP(3)RV) and examined hypoxia-induced augmentation of int racellular Ca2+ in intact cells. Reduced nicotinamide adenine dinucleo tide (NADH) increases IP3-mediated Ca2+ flux in IP(3)RV. This effect i s highly specific for NADH. Hypoxia elicited by brief exposure of nerv e growth factor-differentiated PC12 cells or cerebellar Purkinje cells to cyanide elicits rapid increases in internal [Ca2+], which derives from IP3-sensitive stores. Blockade of this effect by 2-deoxyglucose a nd inhibition of glyceraldehyde-3-phosphate dehydrogenase implicates e nhanced glycolytic production of NADH in the Ca2+ stimulation. Interna l [Ca2+] is markedly and specifically increased by direct intracellula r injection of NADH, and this effect is blocked by heparin, further im plicating IP(3)R stores. These findings indicate that direct regulatio n of IP(3)R by NADH is responsible for elevated cytoplasmic [Ca2+] occ urring in the earliest phase of hypoxia. This link of IP(3)R activity with cellular energy dynamics may be relevant to both hypoxic damage a nd metabolic regulation of IP3 signaling processes.