Kosenko E, Felipo V, Montoliu C, Grisolía S, Kaminsky Y
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Russia.
Metab Brain Dis. 1997 Mar;12(1):69-82. doi: 10.1007/BF02676355.
The effects of hyperammonemia induced in vivo by injecting rats with ammonium acetate on oxidative phosphorylation, malate-aspartate shuttle, some related enzyme activities and metabolite levels in brain mitochondria were studied ex vivo. Rats were found to be either ammonia-sensitive (showing convulsions) or ammonia-resistant (without convulsions) after intraperitoneal injection of ammonium acetate (7 mmol/kg). Ammonium acetate administration to ammonia-sensitive rats led to inhibition of State 3 rates of brain mitochondria utilizing pyruvate, glutamate, isocitrate, and succinate as substrates and to decreased respiratory control index. In brain mitochondria isolated from ammonia-resistant animals, the ammonia-induced effect on such State 3 rates was not observed. In brain mitochondria from hyperammonemic rats without convulsions, a small increase in the activity of malate dehydrogenase was observed; glutamate dehydrogenase, succinate dehydrogenase, and aspartate aminotransferase were not affected. In brain mitochondria from rats with ammonia-induced convulsions, the activities of malate dehydrogenase and succinate dehydrogenase were reduced significantly. Ammonium acetate injection to rats was associated with a 5-fold increase in the brain mitochondrial ammonium ion content and a decrease (ca. 50%) in brain mitochondrial glutamate and aspartate; brain mitochondrial malate and 2-oxoglutarate levels remained unchanged. The rate of the malate-aspartate shuttle in brain mitochondria of hyperammonemic rats was decreased by 20% as compared to corresponding rate in control rats. We conclude that acute administration of ammonium acetate induces serious disturbances in the electron-transport chain, interferences of the malate-aspartate shuttle, alterations of the levels of shuttle intermediates and inhibition of the activities of malate and succinate dehydrogenases in brain mitochondria.
通过给大鼠注射醋酸铵在体内诱导高氨血症，然后离体研究其对脑线粒体氧化磷酸化、苹果酸 - 天冬氨酸穿梭、一些相关酶活性及代谢物水平的影响。给大鼠腹腔注射醋酸铵（7 mmol/kg）后，发现大鼠分为氨敏感型（出现惊厥）和氨耐受型（无惊厥）。给氨敏感型大鼠注射醋酸铵会导致脑线粒体以丙酮酸、谷氨酸、异柠檬酸和琥珀酸为底物时的状态3呼吸速率受到抑制，且呼吸控制指数降低。在从氨耐受型动物分离的脑线粒体中，未观察到氨对这种状态3呼吸速率的影响。在无惊厥的高氨血症大鼠的脑线粒体中，观察到苹果酸脱氢酶活性略有增加；谷氨酸脱氢酶、琥珀酸脱氢酶和天冬氨酸转氨酶未受影响。在有氨诱导惊厥的大鼠的脑线粒体中，苹果酸脱氢酶和琥珀酸脱氢酶的活性显著降低。给大鼠注射醋酸铵与脑线粒体铵离子含量增加5倍以及脑线粒体谷氨酸和天冬氨酸减少（约50%）有关；脑线粒体苹果酸和2-氧代戊二酸水平保持不变。与对照大鼠相应速率相比，高氨血症大鼠脑线粒体中苹果酸 - 天冬氨酸穿梭速率降低了20%。我们得出结论，急性给予醋酸铵会在脑线粒体中引起电子传递链的严重紊乱、苹果酸 - 天冬氨酸穿梭的干扰、穿梭中间体水平的改变以及苹果酸和琥珀酸脱氢酶活性的抑制。
