Li J B, Jefferson L S
Am J Physiol. 1977 Feb;232(2):E243-9. doi: 10.1152/ajpendo.1977.232.2.E243.
The effect of isoproterenol on amino acid concentrations in perfusate and skeletal muscle was studied during a 3-h perfusion of the isolated rat hemicorpus. The beta-adrenergic agonist inhibited the accumulation of alanine, threonine, phenylalanine, tyrosine, lysine, arginine, leucine, and valine and increased the loss of glutamate, aspartate, serine, and isoleucine from the pool of free amino acids in perfusate and muscle. The loss of glutamate was accompanied by a greater accumulation of glutamine. Changes in alanine levels showed the greatest response with a net accumulation of 98 mumol in the controls becoming a net loss of 54 mumol in the experimentals. These changes in amino acid levels were accounted for in part by a 20% decrease in protein degradation. Protein synthesis was not affected by isoproterenol. In addition to an effect on degradation, it appeared that isoproterenol affected amino acid levels by increasing alanine utilization and causing formation of glutamine instead of alanine. Other effects of the drug included increased rates of lactate production, muscle glycogen breakdown, and oxygen consumption, whereas no effects were observed on ATP and creatine phosphate levels. Pyruvate content of muscle was maintained at a higher level in the presence of the drug than in control perfusions.
在对离体大鼠半侧躯体进行3小时灌注期间，研究了异丙肾上腺素对灌注液和骨骼肌中氨基酸浓度的影响。β-肾上腺素能激动剂抑制了丙氨酸、苏氨酸、苯丙氨酸、酪氨酸、赖氨酸、精氨酸、亮氨酸和缬氨酸的积累，并增加了灌注液和肌肉中游离氨基酸池中的谷氨酸、天冬氨酸、丝氨酸和异亮氨酸的损失。谷氨酸的损失伴随着谷氨酰胺的大量积累。丙氨酸水平的变化表现出最大的反应，对照组中净积累98微摩尔，而实验组中变为净损失54微摩尔。氨基酸水平的这些变化部分是由于蛋白质降解减少了20%。蛋白质合成不受异丙肾上腺素的影响。除了对降解有影响外，异丙肾上腺素似乎还通过增加丙氨酸的利用并导致谷氨酰胺而非丙氨酸的形成来影响氨基酸水平。该药物的其他作用包括乳酸生成率增加、肌肉糖原分解和耗氧量增加，而对ATP和磷酸肌酸水平未观察到影响。在药物存在的情况下，肌肉中的丙酮酸含量维持在比对照灌注更高的水平。
