Mozdziak P E, Greaser M L, Schultz E
Department of Anatomy, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA.
J Appl Physiol (1985). 1998 Apr;84(4):1359-64. doi: 10.1152/jappl.1998.84.4.1359.
The relationship between myogenin or MyoD expression and hypertrophy of the rat soleus produced either by clenbuterol and 3,3', 5-triiodo-L-thyronine (CT) treatment or by surgical overload was examined. Mature female rats were subjected to surgical overload of the right soleus with the left soleus serving as a control. Another group received the same surgical treatment but were administered CT. Soleus muscles were harvested 4 wk after surgical overload and weighed. Myosin heavy chain isoforms were separated by using polyacrylamide gel electrophoresis while myogenin and MyoD expression were evaluated by Northern analysis. CT and functional overload increased soleus muscle weight. CT treatment induced the appearance of the fast type IIX myosin heavy chain isoform, depressed myogenin expression, and induced MyoD expression. However, functional overload did not alter myogenin or MyoD expression in CT-treated or non-CT-treated rats. Thus pharmacologically and surgically induced hypertrophy have differing effects on myogenin and MyoD expression, because their levels were associated with changes in myosin heavy chain composition (especially type IIX) rather than changes in muscle mass.
研究了肌细胞生成素或MyoD表达与大鼠比目鱼肌肥大之间的关系，该肥大由克伦特罗和3,3',5-三碘-L-甲状腺原氨酸（CT）处理或手术过载引起。成年雌性大鼠右比目鱼肌进行手术过载，左比目鱼肌作为对照。另一组接受相同的手术处理，但给予CT。手术过载4周后收获比目鱼肌并称重。使用聚丙烯酰胺凝胶电泳分离肌球蛋白重链异构体，同时通过Northern分析评估肌细胞生成素和MyoD表达。CT和功能过载增加了比目鱼肌重量。CT处理诱导了快速型IIX肌球蛋白重链异构体的出现，抑制了肌细胞生成素表达，并诱导了MyoD表达。然而，功能过载在CT处理或未处理的大鼠中并未改变肌细胞生成素或MyoD表达。因此，药理学和手术诱导的肥大对肌细胞生成素和MyoD表达有不同影响，因为它们的水平与肌球蛋白重链组成（尤其是IIX型）的变化而非肌肉质量的变化相关。
