申传安 柴家科 姚咏明 盛志勇

    【摘要】 目的 研究地塞米松对体外培养的骨骼肌肌管内长寿命蛋白降解的影响及其可能的作用机制。方法 无菌分离(2日龄)Wistar大鼠双下肢肌肉，组织块法培养、增殖、传代纯化成肌细胞，融合形成肌管，使用L 〔3,5 3H〕酪氨酸标记肌管长寿命蛋白后，随机分成两组。A组：分别用不含地塞米松(对照组)或含地塞米松10 nmol/L(A1组)、100 nmol/L(A2组)、1 000 nmol/L(A3组)的培养液培养肌管，12、24、36和48 h后使用液体闪烁计数仪测定培养液和细胞内L 〔3,5 3H〕 酪氨酸的含量，计算肌管长寿命蛋白的降解率。B组：分别用含蛋白酶体抑制剂MG132(50 μmol/L，B1组)或含MG132(50 μmol/L)和地塞米松100 nmol/L(B2组)的培养液培养肌管24 h，相同方法测定肌管长寿命蛋白降解率。结果A1、A2和A3组长寿命蛋白降解率均较对照组显著增加，差异有显著性(P均<0.01)。A2组和A3组长寿命蛋白降解率均较A1组显著增加，差异有显著性(P均<0.01)。A2组和A3组比较，长寿命蛋白降解率差异无显著性(P>0.05)。B1组长寿命蛋白降解率较对照组(24 h)降低明显，B2组长寿命蛋白降解率较A2组(24 h)显著降低，差异均有显著性(P均<0.01)。结论 泛素蛋白酶体途径是骨骼肌肌管长寿命蛋白的重要降解途径之一。地塞米松能通过激活肌管内泛素蛋白酶体途径而增强长寿命蛋白的降解，此效应在一定范围内呈量效依赖关系。

    【关键词】 蛋白降解；肌管；骨骼肌；地塞米松；蛋白酶体抑制剂；MG132

    Effect of dexamethasone on degradation of cultured myotube protein and its mechanism SHEN Chuanan, CHAI Jiake, YAO Yongming, SHENG Zhiyong. Burns Institute, the First Affiliated Hospital of General Hospital of PLA (Formerly 304 th Hospital of PLA), Beijing 100037, China

    【Abstract】 Objective To study the effect of dexamethasone on degradation of longlived protein in myotubes and to elucidate its possible mechanism. Methods After isolating skeletal muscles of rat′s hind limb under sterile condition, the myoblasts were proliferated in tissueblock culture. After being passaged and purified, the myoblasts fused into myotubes. The protein in myotubes was radiolabelled with L〔3,53H〕tyrosine, and then the myotubes were divided into two groups. In group A,the myotubes were cultured in Dubbecco′s modified Eagle′s medium (DMEM) containing 10% fetal bovine serum (FBS) and 2 mmol/L tyrosine without dexamethasone (control group), with dexamethasone 10 nmol/L(group A1), dexamethasone 100 nmol/L(group A2), and dexamethasone 1 000 nmol/L(group A3) ......