Henriksen E J, Ritter L S
Department of Exercise and Sport Sciences, University of Arizona, Tucson 85721.
J Appl Physiol (1985). 1993 Aug;75(2):820-4. doi: 10.1152/jappl.1993.75.2.820.
We have previously demonstrated that mechanical unweighting of the soleus muscle by hindlimb suspension leads to increases in insulin receptor binding, muscle/fat-specific glucose transporter (GLUT-4) protein levels, and insulin-stimulated glucose transport activity. The present study used a novel approach to further evaluate the potential role of postreceptor binding mechanisms in this enhanced insulin effect after unweighting. Insulin-like growth factor I (IGF-I), vanadate, and phospholipase C were used to stimulate glucose transport activity independently of insulin receptor binding. Soleus glucose transport activity (assessed by 2-deoxyglucose uptake) was evaluated in vitro with soleus strips (approximately 18 mg). Progressively increased responses to maximally effective doses of insulin or IGF-I were observed after 3 and 6 days of unweighting compared with weight-matched control strips. Enhanced maximal responses to vanadate (6 days only) and phospholipase C (3 and 6 days) for 2-deoxyglucose uptake were also observed. The results of this study 1) provide evidence that post-insulin receptor binding mechanisms also play a role in the enhanced response of the insulin-dependent pathway for stimulation of glucose transport in unweighted skeletal muscle and 2) indicate that IGF-I action on glucose transport is included in this enhanced response in unweighted muscle.
我们之前已经证明，后肢悬吊导致比目鱼肌机械性失重会使胰岛素受体结合增加、肌肉/脂肪特异性葡萄糖转运蛋白（GLUT-4）水平升高以及胰岛素刺激的葡萄糖转运活性增强。本研究采用一种新方法，进一步评估受体后结合机制在失重后这种增强的胰岛素效应中的潜在作用。胰岛素样生长因子I（IGF-I）、钒酸盐和磷脂酶C被用于独立于胰岛素受体结合来刺激葡萄糖转运活性。用比目鱼肌条（约18毫克）体外评估比目鱼肌葡萄糖转运活性（通过2-脱氧葡萄糖摄取评估）。与体重匹配的对照肌条相比，失重3天和6天后观察到对最大有效剂量胰岛素或IGF-I的反应逐渐增加。对于2-脱氧葡萄糖摄取，还观察到对钒酸盐（仅6天）和磷脂酶C（3天和6天）的最大反应增强。本研究结果1）提供了证据，表明胰岛素受体后结合机制在失重骨骼肌中胰岛素依赖性葡萄糖转运刺激途径的增强反应中也起作用，2）表明IGF-I对葡萄糖转运的作用包含在失重肌肉的这种增强反应中。
