Nitric oxide-mediated Ca++-influx in neuronal nuclei and cortical synaptosomes of normoxic and hypoxic newborn piglets.
Previous studies have shown that hypoxia results in the generation of nitric oxide (NO) free radicals in the cerebral cortex of newborn animals. The present study tested the hypothesis that NO increases Ca++-influx in neuronal nuclei as well as N-methyl-D aspartate (NMDA) receptor-mediated Ca++-influx in cortical synaptosomes of newborn piglets. Studies were performed in five normoxic (Nx) and 6 hypoxic (Hx) newborn piglets. Cerebral tissue hypoxia was documented by determining the levels of ATP and phosphocreatine (PCr). 45Ca++ -influx was determined in the presence of sodium nitroprusside (SNP, 10 microM), a NO donor, and peroxynitrite (10 microM). In the Hx group, ATP levels decreased to 1.40+or-0.69 vs 4.27+or-0.80 micromoles/g brain in the Nx group (P<0.05). Similarly, PCr levels decreased to 0.91+or-0.57 vs 3.40+or-0.99 micromoles/g brain (P<0.001). Nuclear 45Ca++-influx increased from 3.57+or-1.46 pmoles/mg protein in Nx nuclei to 8.64+or-3.50 in Hx nuclei (P<0.05). SNP increased neuronal nuclear Ca++ influx in the Nx from 3.57+or-1.46 to 5.47+or-2.52 pmoles/mg protein (P<0.05) but did not affect Ca++ influx in the Hx group (8.64+or-3.50 vs. 10.17+or-4.00 pmoles/mg protein). The level of Ca++ influx in the presence of SNP in Nx nuclei was similar to that seen in Hx nuclei alone. Peroxynitrite did not affect nuclear Ca++-influx in either Nx or Hx group. Synaptosomal Ca++-influx in the presence of glu + gly was 40+or-11 pmoles/mg protein in the Nx group and 80+or-16 pmoles/mg protein in the Hx group (P<0.05). Both SNP and peroxynitrite increased Ca++ influx in Nx and Hx synaptosomes. These results show that hypoxia results in increased nuclear and synaptosomal Ca++-influx. Further, the data demonstrate that NO increases intranuclear as well as intrasynaptosomal Ca++-influx and suggest that during hypoxia, the increase in intranuclear and intraynaptosomal Ca++ is NO-mediated. We propose that NO-mediated modification (by nitrosylation/nitration) of nuclear membrane high affinity Ca++-ATPase and neuronal membrane NMDA receptor, resulting in increased intranuclear and intracellular Ca++ influx, are potential NO-mediated mechanisms of Hx neuronal injury.
Mishra
Om Prakash
OP
Department of Pediatrics, MCP Hahnemann School of Medicine and St. Chrtistopher's, Hospital for Children, Philadelphia, PA, USA.
Delivoria-Papadopoulos
Maria
M
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001238:Asphyxia Neonatorum / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism* / Q000473:pathology; D002540:Cerebral Cortex / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D005609:Free Radicals; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D005998:Glycine / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D002534:Hypoxia, Brain / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D007231:Infant, Newborn; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009474:Neurons / Q000378:metabolism* / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology; D030421:Peroxynitrous Acid / Q000378:metabolism / Q000494:pharmacology; D010725:Phosphocreatine / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000378:metabolism; D013552:Swine; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
D005609:Free Radicals; D020030:Nitric Oxide Donors; D016194:Receptors, N-Methyl-D-Aspartate; D010725:Phosphocreatine; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; D018698:Glutamic Acid; D000255:Adenosine Triphosphate; D002118:Calcium; D005998:Glycine