Fluckey J D, Vary T C, Jefferson L S, Farrell P A
Noll Physiological Research Center, University Park, Pennsylvania 16802, USA.
Am J Physiol. 1996 Feb;270(2 Pt 1):E313-9. doi: 10.1152/ajpendo.1996.270.2.E313.
This study investigated whether insulin has a modulatory effect on protein synthesis rates in skeletal muscle after four sessions of resistance exercise. Male rats engaged in resistance exercise (Acute) that required full extension of the hindlimbs with weights over the scapula or performed the standing movement with no additional weight (Nonex). Two separate studies were conducted. Rates of protein synthesis for study 1 (Acute, n = 6; Nonex, n = 6) were assessed 16 h postexercise by incorporation of [3H]phenylalanine ([3H]F) into muscle protein by use of an in vivo flooding dose protocol. Rates of protein synthesis in soleus of Acute (100 +/- 9 nmol F.g-1.h-1) were significantly higher than in Nonex (72 +/- 9 nmol F.g-1.h-1, P < 0.05). Rates of protein synthesis were significantly higher in gastrocnemius of Acute vs. Nonex (48 +/- 7 vs. 25 +/- 2 nmol F.g-1.h-1) but not in extensor digitorum longus (EDL). Assessment of protein synthesis rates for study 2 was conducted 16 h after resistance exercise with use of [3H]F incorporation into muscle protein during in situ bilateral hindlimb perfusion, with each leg perfused simultaneously but separately. Perfusion medium for one leg, but not the other, contained insulin (6.25 ng/ml). Soleus and gastrocnemius of Acute had higher protein synthesis rates than Nonex only in the leg that received insulin. For gastrocnemius, rates of protein synthesis in Acute without insulin were significantly lower than in Nonex with or without insulin. Insulin had no effect on protein synthesis rates for any muscle in Nonex rats. Neither exercise nor insulin affected protein synthesis rates in EDL. We conclude that insulin is a necessary component in elevated protein synthesis rates after resistance exercise in muscles composed of primarily slow-or fast-twitch fibers, and that a physiological perturbation (resistance exercise in this study) is required to observe such modulation, because rates of protein synthesis in Nonex muscles were not influenced by insulin.
本研究调查了在进行四组抗阻运动后，胰岛素是否对骨骼肌中的蛋白质合成速率具有调节作用。雄性大鼠进行抗阻运动（急性组），该运动要求后肢在负重超过肩胛骨的情况下完全伸展，或者进行无额外负重的站立运动（无负重组）。进行了两项独立研究。研究1（急性组，n = 6；无负重组，n = 6）在运动后16小时，通过采用体内饱和剂量方案将[3H]苯丙氨酸（[3H]F）掺入肌肉蛋白来评估蛋白质合成速率。急性组比目鱼肌的蛋白质合成速率（100±9 nmol F·g-1·h-1）显著高于无负重组（72±9 nmol F·g-1·h-1，P < 0.05）。急性组腓肠肌的蛋白质合成速率显著高于无负重组（48±7 vs. 25±2 nmol F·g-1·h-1），但在趾长伸肌（EDL）中则不然。研究2的蛋白质合成速率评估是在抗阻运动后16小时，通过在原位双侧后肢灌注期间将[3H]F掺入肌肉蛋白来进行的，每条腿同时但分别灌注。一条腿的灌注液中含有胰岛素（6.25 ng/ml），而另一条腿没有。仅在接受胰岛素的腿中，急性组比目鱼肌和腓肠肌的蛋白质合成速率高于无负重组。对于腓肠肌，未接受胰岛素的急性组蛋白质合成速率显著低于接受或未接受胰岛素的无负重组。胰岛素对无负重组大鼠的任何肌肉的蛋白质合成速率均无影响。运动和胰岛素均未影响EDL的蛋白质合成速率。我们得出结论，胰岛素是主要由慢肌纤维或快肌纤维组成的肌肉在抗阻运动后蛋白质合成速率升高的必要组成部分，并且需要生理扰动（本研究中的抗阻运动）来观察这种调节作用，因为无负重组肌肉的蛋白质合成速率不受胰岛素影响。
