Tischler M E, Henriksen E J, Cook P H
Department of Biochemistry, University of Arizona Health Sciences Center, Tucson 85724.
Muscle Nerve. 1988 Jul;11(7):752-6. doi: 10.1002/mus.880110711.
The influence of glucocorticoids on muscle glutamine production in starvation was studied by using cortisol-treated or non-cortisol-treated, starved, adrenalectomized rats. Administration of cortisol at physiological doses in vivo (1 mg/100 g body weight) to fasted, adrenalectomized rats increased the muscle ratio of glutamine/glutamate and the activity of glutamine synthetase after only 6 hours. Prior treatment of fasted, adrenalectomized animals with actinomycin D or proflavine abolished these increases by cortisol. Therefore, cortisol induces muscle glutamine synthetase, and this induction can be detected by changes in the fresh-muscle ratio of glutamine/glutamate. Using this ratio as a qualitative indicator of muscle glutamine synthesis, the role of glucocorticoids in modifying muscle glutamine production in starvation was studied. In fresh-frozen soleus, extensor digitorum longus, and diaphragm muscle, starvation led to greater ratios of glutamine/glutamate and higher levels of tyrosine, which are indicative of enhanced muscle protein turnover. These effects were not apparent in starved, adrenalectomized animals but were restored, at least partially, by administering a physiological dose of cortisol. Therefore, glucocorticoids seem essential for promoting muscle glutamine production in starvation probably by inducing the activity of glutamine synthetase.
通过使用经皮质醇处理或未经皮质醇处理的饥饿去肾上腺大鼠，研究了糖皮质激素对饥饿状态下肌肉谷氨酰胺生成的影响。对禁食的去肾上腺大鼠体内给予生理剂量的皮质醇（1毫克/100克体重），仅6小时后，肌肉中谷氨酰胺/谷氨酸的比例以及谷氨酰胺合成酶的活性就增加了。用放线菌素D或原黄素预先处理禁食的去肾上腺动物，可消除皮质醇引起的这些增加。因此，皮质醇诱导肌肉谷氨酰胺合成酶，并且这种诱导可以通过新鲜肌肉中谷氨酰胺/谷氨酸比例的变化来检测。以该比例作为肌肉谷氨酰胺合成的定性指标，研究了糖皮质激素在饥饿状态下调节肌肉谷氨酰胺生成中的作用。在新鲜冷冻的比目鱼肌、趾长伸肌和膈肌中，饥饿导致谷氨酰胺/谷氨酸的比例更高，酪氨酸水平更高，这表明肌肉蛋白质周转增强。这些作用在饥饿的去肾上腺动物中不明显，但通过给予生理剂量的皮质醇至少部分恢复。因此，糖皮质激素可能通过诱导谷氨酰胺合成酶的活性，对于促进饥饿状态下肌肉谷氨酰胺的生成似乎至关重要。
