title: Effects of ammonia and beta-methylene-DL-aspartate on the oxidation of glucose and pyruvate by neurons and astrocytes in primary culture.
abstract: Both ammonia and beta-methylene-DL-aspartate (beta-MA), an irreversible inhibitor of aspartate aminotransferase activity and thus of the malate-aspartate shuttle, were found previously to decrease oxidative metabolism in cerebral cortex slices. In the present work, the possibility that ammonia and beta-MA affect energy metabolism by a common mechanism (i.e., via inhibition of the malate-aspartate shuttle) was investigated using primary cultures of neurons and astrocytes. Incubation of astrocytes for 30 min with 5 mM beta-MA resulted in a decreased production of 14CO2 from [U-14C]glucose, but did not affect 14CO2 production from [2-14C]pyruvate. Conversely, incubation of astrocytes with 3 mM ammonium chloride resulted in decreased 14CO2 production from [2-14C]pyruvate, but 14CO2 production from [U-14C]glucose was not significantly affected. Ammonium chloride had no significant effect on 14CO2 production from either [U-14C]glucose or [2-14]pyruvate by neurons. However, incubation of neurons with beta-MA or beta-MA plus ammonium chloride resulted in a approximately 45% decrease of 14CO2 production from both [U-14C]glucose and [2-14C]pyruvate. A 2-h incubation of astrocytes with beta-MA resulted in no change in ATP levels, but a 35% decrease in phosphocreatine. Similar treatment of neurons resulted in greater than 50% decrease in ATP, but had little effect on phosphocreatine. beta-MA also caused a decrease in glutamate and aspartate content of neurons, but not of astrocytes. The different metabolic responses of neurons and astrocytes towards beta-MA were probably not due to a differential inhibition of aspartate aminotransferase which was inhibited by approximately 45% in astrocytes and by approximately 55% in neurons.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000643:Ammonium Chloride / Q000494:pharmacology*; D000818:Animals; D001219:Aspartate Aminotransferases / Q000037:antagonists & inhibitors; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002478:Cells, Cultured; D004734:Energy Metabolism / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D051379:Mice; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010725:Phosphocreatine / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism*; D019289:Pyruvic Acid
chemical_list: D011773:Pyruvates; D000643:Ammonium Chloride; D010725:Phosphocreatine; D002245:Carbon Dioxide; D001224:Aspartic Acid; C036683:beta-methyleneaspartate; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D001219:Aspartate Aminotransferases; D005947:Glucose