Andersen N B, Andreassen T T, Orskov H, Oxlund H
Department of Connective Tissue Biology, Institute of Anatomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
Eur J Endocrinol. 2000 Sep;143(3):409-18. doi: 10.1530/eje.0.1430409.
A decline of skeletal muscle mass and strength is seen with aging and immobilization. Growth hormone (GH) has been shown to increase muscle mass. In the present study the effects of a combination of mild exercise and GH on skeletal musculature tetanic tension, dry defatted weight (DDW), volume, water, fat and collagen concentrations were investigated in old rats.
Recombinant human GH (2.7mg/kg per day) was injected subcutaneously for 73 days in 21-month-old female rats. Exercised rats ran on a treadmill, 8 m/min for 1 h/day. The in vivo maximal tetanic tension of the calf musculature (m. soleus, m. plantaris, m. gastrocnemius together) was analysed in anaesthetized rats by stimulating the ischiadic nerve.
The maximal tetanic tension was increased by 23% in GH-injected compared to saline-injected rats. Mild exercise + GH in combination resulted in a further 18% increase in maximal tetanic tension. The mild exercise by itself did not influence the maximal tetanic tension significantly when compared with saline injected rats. The GH administration and/or mild exercise did not change skeletal muscle endurance, measured as tetanic tension during 30s of stimulation. Serum IGF-I concentration was increased twofold in GH-injected rats.
The increased muscle mass induced by GH + mild exercise was associated with a corresponding increase in maximal tetanic tension. Combination of GH + mild exercise resulted in a substantial further increase of muscle mass and maximal tension compared with GH injections alone in these old rats.
随着衰老和肢体固定，骨骼肌质量和力量会下降。生长激素（GH）已被证明可增加肌肉质量。在本研究中，研究了轻度运动与生长激素联合应用对老年大鼠骨骼肌强直张力、去脂干重（DDW）、体积、水分、脂肪和胶原蛋白浓度的影响。
对21月龄雌性大鼠皮下注射重组人生长激素（每天2.7mg/kg），持续73天。运动组大鼠在跑步机上以8m/min的速度跑步，每天1小时。通过刺激坐骨神经，在麻醉大鼠中分析小腿肌肉（比目鱼肌、跖肌、腓肠肌总和）的体内最大强直张力。
与注射生理盐水的大鼠相比，注射生长激素的大鼠最大强直张力增加了23%。轻度运动与生长激素联合应用使最大强直张力进一步增加了18%。与注射生理盐水的大鼠相比，单纯轻度运动对最大强直张力没有显著影响。生长激素给药和/或轻度运动并未改变以30秒刺激期间的强直张力衡量的骨骼肌耐力。注射生长激素的大鼠血清IGF-I浓度增加了两倍。
生长激素 + 轻度运动诱导的肌肉质量增加与最大强直张力的相应增加相关。与单独注射生长激素相比，生长激素 + 轻度运动联合应用使这些老年大鼠的肌肉质量和最大张力大幅进一步增加。
