α-肾上腺素能刺激对分离的大鼠肝细胞谷氨酰胺代谢的影响
Alpha-adrenergic stimulation of glutamine metabolism in isolated rat hepatocytes.
作者信息
Verhoeven A J, Estrela J M, Meijer A J
出版信息
Biochem J. 1985 Sep 1;230(2):457-63. doi: 10.1042/bj2300457.
The mechanisms by means of which phenylephrine stimulates glutamine metabolism were studied in isolated rat hepatocytes. In the first 2 min after phenylephrine addition there was a rapid fall in the concentrations of intracellular 2-oxoglutarate and glutamate, presumably owing to activation of 2-oxoglutarate dehydrogenase. This was followed 2-3 min later by activation of glutaminase and by increases in glutamate and 2-oxoglutarate. Activation of glutaminase by phenylephrine was due to direct stimulation of the enzyme rather than to reversal of inhibition by the decrease in 2-oxoglutarate and glutamate. The stimulation of glutaminase by phenylephrine is partly due to an increase in the affinity of the enzyme for ammonia, its essential activator. It is concluded that stimulation of steady-state flux through the pathway from glutamine to glucose and urea can only be achieved by stimulation of glutaminase, the first enzyme in the pathway.
在分离的大鼠肝细胞中研究了去氧肾上腺素刺激谷氨酰胺代谢的机制。添加去氧肾上腺素后的最初2分钟内，细胞内2-氧代戊二酸和谷氨酸的浓度迅速下降，这可能是由于2-氧代戊二酸脱氢酶的激活。2-3分钟后，谷氨酰胺酶被激活，谷氨酸和2-氧代戊二酸增加。去氧肾上腺素对谷氨酰胺酶的激活是由于对该酶的直接刺激，而不是由于2-氧代戊二酸和谷氨酸减少导致的抑制作用的逆转。去氧肾上腺素对谷氨酰胺酶的刺激部分是由于该酶对其必需激活剂氨的亲和力增加。得出的结论是，只有通过刺激谷氨酰胺酶（该途径中的第一种酶），才能实现通过从谷氨酰胺到葡萄糖和尿素的途径的稳态通量的刺激。
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