Essén-Gustavsson B, Blomstrand E
Department of Large Animal Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Acta Physiol Scand. 2002 Mar;174(3):275-81. doi: 10.1046/j.1365-201x.2002.00942.x.
A few animal studies have shown that some amino acid concentrations vary between different muscle fibre types. In the present study, amino acid concentrations were measured in separate pools of different fibre types in human skeletal muscle, with reduced glycogen stores, before and after sustained exercise. Five subjects exercised at a submaximal work rate for 60 min and then at a maximal rate for 20 min. Biopsy samples were taken from the vastus lateralis muscle before and after exercise; they were freeze-dried and individual fibres were dissected out. Fragments of these fibres were stained for myosin-adenosine triphosphatase (ATPase) and identified as type I or type II fibres. The concentrations of free amino acids were measured by high performance liquid chromatography (HPLC) in perchloric acid (PCA) extracts containing pools of either type of fibre. After exercise, glycogen was decreased in type I fibres (53%) and in four subjects also in type II fibres. The concentrations of most amino acids were similar in the two fibre types before exercise, but the glutamate, aspartate and arginine levels were 10% higher in type II than in type I fibres. After exercise, the glutamate concentration was decreased by 45% in both fibre types and the branched-chain amino acids (BCAA) were decreased in type II fibres (14%). Exercise caused an increase by 25-30% in tyrosine concentration in both type I and type II fibres. The results show that amino acids can be measured in pools of fibre fragments and suggest that amino acid metabolism play an important role in both type I and type II fibres during exercise.
一些动物研究表明，不同肌肉纤维类型之间的某些氨基酸浓度存在差异。在本研究中，对糖原储备减少的人体骨骼肌中不同纤维类型的单独样本池，在持续运动前后的氨基酸浓度进行了测量。五名受试者先以次最大工作强度运动60分钟，然后以最大强度运动20分钟。在运动前后从股外侧肌采集活检样本；将样本冷冻干燥并分离出单根纤维。这些纤维的片段用肌球蛋白 - 三磷酸腺苷酶（ATPase）染色，并鉴定为I型或II型纤维。通过高效液相色谱法（HPLC）在含有任一类型纤维样本池的高氯酸（PCA）提取物中测量游离氨基酸的浓度。运动后，I型纤维中的糖原减少（53%），在四名受试者中II型纤维中的糖原也减少。运动前两种纤维类型中大多数氨基酸的浓度相似，但II型纤维中的谷氨酸、天冬氨酸和精氨酸水平比I型纤维高10%。运动后，两种纤维类型中的谷氨酸浓度均降低了45%，II型纤维中的支链氨基酸（BCAA）减少了（14%）。运动使I型和II型纤维中的酪氨酸浓度均增加了25 - 30%。结果表明，可以在纤维片段样本池中测量氨基酸，并表明氨基酸代谢在运动期间的I型和II型纤维中均起重要作用。
