Anderson P T, Helferich W G, Parkhill L C, Merkel R A, Bergen W G
Department of Animal Science, Michigan State University, East Lansing 48824.
J Nutr. 1990 Dec;120(12):1677-83. doi: 10.1093/jn/120.12.1677.
The ability of the phenethanolamine (beta-adrenergic agonist) ractopamine to stimulate cellular protein accretion and protein synthesis in cultured muscle cells was evaluated. ELC5 myoblasts (a subclone of rat L6 cells) were proliferated in culture (Dulbecco's Modified Eagle Medium plus 10% fetal bovine serum at 37 degrees C) to confluency and then allowed to differentiate to form myotubes. Myotubes were then further incubated in the presence of 10(-9), 10(-8), 10(-7), 10(-6) or 10(-5) mol/L ractopamine. A significant (p less than 0.05) response in cellular protein accretion was observed for the 10(-6) and 10(-5) concentrations when compared to 10(-8) and 10(-9) mol/L ractopamine. Ractopamine at 0 and 10(-6) mol/L was used to examine the effect of the beta agonist on [35S]methionine incorporation (protein synthesis) into total cellular protein, 43-kDa proteins and myosin heavy-chain (200 kDa) protein. Protein synthesis in response to beta agonist treatment was measured at 4, 24, 48, 72 and 96 h after ractopamine addition to the ELC5 myotubes in culture. Ractopamine (10(-6) mol/L) increased [35S]methionine incorporation (apparent protein synthesis) at 24 h (p less than 0.01), 48 h (p less than 0.05), 72 h (p less than 0.01) and 96 h (p less than 0.05) in cultured ELC5 muscle cells. Ractopamine also increased apparent protein synthesis rate of the 43-kDa proteins (p less than 0.05) and myosin heavy-chain protein (200 kDa) (p less than 0.05). These results indicate that ractopamine-enhanced ELC5 myotube protein accretion is mediated, at least in part, by stimulating cellular protein synthesis.
评估了苯乙醇胺（β-肾上腺素能激动剂）莱克多巴胺刺激培养的肌肉细胞中细胞蛋白质积聚和蛋白质合成的能力。ELC5成肌细胞（大鼠L6细胞的一个亚克隆）在培养物中（在37℃下，于杜氏改良 Eagle 培养基加10%胎牛血清）增殖至汇合，然后使其分化形成肌管。然后将肌管在10⁻⁹、10⁻⁸、10⁻⁷、10⁻⁶或10⁻⁵mol/L莱克多巴胺存在下进一步孵育。与10⁻⁸和10⁻⁹mol/L莱克多巴胺相比，在10⁻⁶和10⁻⁵浓度下观察到细胞蛋白质积聚有显著（p<0.05）反应。使用0和10⁻⁶mol/L的莱克多巴胺来检查β激动剂对[³⁵S]甲硫氨酸掺入（蛋白质合成）到总细胞蛋白质、43 kDa蛋白质和肌球蛋白重链（200 kDa）蛋白质中的影响。在将莱克多巴胺添加到培养的ELC5肌管中后的4、24、48、72和96小时测量对β激动剂处理的蛋白质合成。莱克多巴胺（10⁻⁶mol/L）在24小时（p<0.01）、48小时（p<0.05）、72小时（p<0.01）和96小时（p<0.05）增加了培养的ELC5肌肉细胞中[³⁵S]甲硫氨酸掺入（表观蛋白质合成）。莱克多巴胺还增加了43 kDa蛋白质（p<0.05）和肌球蛋白重链蛋白质（200 kDa）（p<0.05）的表观蛋白质合成速率。这些结果表明，莱克多巴胺增强的ELC5肌管蛋白质积聚至少部分是通过刺激细胞蛋白质合成介导的。
