中文摘要：

目的观察胰岛素对体外培养兔骨骼肌肌管蛋白降解的调节作用。方法无菌分离幼兔下肢骨骼肌肌肉，采用组织块法分离、培养成肌细胞，待其融合形成肌管，采用L-[3，5-^3H]．酪氨酸标记肌管内蛋白后，随机分为对照组（用含体积分数10％胎牛血清的DMEM培养液培养）、胰岛素组（用含100nmoL／L胰岛素＋体积分数10％胎牛血清的DMEM培养液培养）、地塞米松组（用含100nmoL／L地塞米松＋体积分数10％胎牛血清的DMEM培养液培养）和胰岛素＋地塞米松组（用含100nmol／L胰岛素＋100nmol／L地塞米松＋体积分数10％胎牛血清的DMEM培养液培养），每组含24孔肌管。培养24h后，应用液体闪烁计数仪测定培养液和肌管内L-[3，5-^3H]．酪氨酸的含量，计算肌管内蛋白的降解率。RNA印迹法测定肌管内泛素-蛋白酶体C2亚基mRNA的表达水平，以其与内参照甘油醛-3-磷酸脱氢酶的灰度值之比表示。结果肌管内蛋白的降解比：地塞米松组为0．50±0．03，明显高于对照组（0．38±0．04，P〈0．01）；胰岛素组为0．35±0．03，明显低于对照组（P〈0．05）；胰岛素＋地塞米松组为0．41±0．03，明显低于地塞米松组（P〈0．01），但仍高于对照组（P〈0．05）。肌管内泛素-蛋白酶体C2亚基的mRNA表达水平：与对照组（泛素2．4kb条带为0．82±0．15、1．2kb条带为0．60±0．10，C2亚基为0．75±0．16）比较，地塞米松组（泛素2．4kb条带为2．15±0．23、1．2kb条带为1．50±0．14，C2亚基为1．50±0．13）明显升高（P〈0．01）；胰岛素＋地塞米松组（泛素2．4kb条带为1．25±0．17、1．2kb条带为0．85±0．09，C2亚基为0．90±0．15）明显低于地塞米松组（P〈0．01）；胰岛素组（泛素2．4kb条带为0．85±0．07、1．2kb条带为0．65±0．12，C2亚基为0．76±0．09）与对照组相近（P〉0．05）。结论胰岛素对兔骨骼肌肌管内?

英文摘要：

Objective To study the effects of insulin on the proteolysis of cultured rabbit skeletal muscular myotubes in vitro, and their possible mechanisms. Methods Muscles of lower limbs of juvenile rabbits were isolated for tissue-block culture. After passage, myoblasts were formed and fused into myotubes. Then the protein in myotubes was radiolabelled with L-[ 3,5-^3H ] tyrosine. The myotubes were cultured in DMEM medium containing 100 nmol/L insulin （n = 24, group B） , 100 nmol/L dexamethasone （n =24, group C）, 100 nmol/L insulin and 100 nmol/L dexamethasone （n = 24, group D）, no insulin or dexamethasone （ n = 24, group A）, respectively. Twenty-four hours after culture, the L- [ 3,5-^3 H ] tyrosine content in culture medium and cells were determined, and the degradation rates of protein were calculated. The mRNA expressions of ubiquitin and protease C2 subunit were determined by Northern blot. Results The degradation rates of myotube protein in group A （0.38 ± 0.04） was obviously lower than that in group C （0.50±0.03, P 〈0.01）, but it was obviously higher than that in group B（0.35 ±0.03, P 〈0.05）. Though the degradation rates of myotube protein in group D （0.41 ±0.03） was evidently lower than that in group C（ P 〈 0.01 ） , it was still higher than that in group A（ P 〈 0.05）. The mRNA expressions of ubiquitin and protease C2 subunit in group A（ the scale： 2.4 kb ubiquitin was 0.82 ± 0. 15, 1.2 kb ubiquitin was 0.60 ±0.10,C2 subunit was 0.75 ±0.16） was obviously lower than that in group C （the scale： 2.4 kb ubiquitin was 2.15 ±0.23, 1.2 kb ubiquitin was 1.50 ±0.14,C2 subunit was 1.50 ±0.13 , P 〈0.01） , but it in group D was lower than that in group C （the scale： 2.4 kb ubiquitin was 1.25 ±0.17, 1.2 kb abiquitin was 0.85±0.09, C2 subunit was 0.90±0.15, P〈0.01）, and it was similar to that in group B （the scale： 2.4 kb ubiquitin was 0.85±0.07, 1.2 kb ubiquitin was 0.65±0.12, C2 subunit was 0.76±0.09, P〉0.05）. Conclusion The effec