Coordinated expression of myosin heavy chain isoforms and metabolic enzymes within overloaded rat muscle fibers
Coordinated expression of myosin heavy chain isoforms and metabolic enzymes within overloaded rat muscle fibers
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DOI：
10.1152/ajpcell.1997.273.2.c371
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发表时间：
1997-08-01
影响因子：
5.5
通讯作者：
Michel, RN
中科院分区：
文献类型：
--
作者：
Dunn, SE;Michel, RN
我们研究了肌球蛋白重链（MHC）和代谢酶在个体超载成年大鼠跖纤维中的协调调节。这是通过针对不同发育和成人mhc的单克隆抗体，以及定量显微光度琥珀酸脱氢酶（SDH）和甘油-3-磷酸脱氢酶（GPDH）酶测定来完成的。超载使MHC表达按IIb—> IIx—> IIa—> α /I的顺序移位，同时，共表达I和α -MHC的细胞增加了两倍，并且在先前存在的肌纤维中短暂地重新表达了两种胚胎MHC和新生儿同种异构体。过载导致所有细胞类型的GPDH活性迅速下降50%，与大小无关，并在6周后恢复。纤维SDH活性根据MHC组成而变化，例如，共表达IIa MHC的过载纤维显示出控制缓慢的纤维SDH水平，而表达IIx和IIb MHC的细胞显示出短暂的30%的SDH增加，并在6周后恢复。我们的研究结果表明，在过载期间，纤维逐渐适应新的功能需求，并显示出更有效的细胞能量利用和传递特性。适应的时间过程表明糖酵解酶在这些转变的开始中起作用。
We studied the coordinated regulation of myosin heavy chains (MHC) and metabolic enzymes within individual overloaded adult rat plantaris fibers. This was done using monoclonal antibodies raised against distinct developmental and adult MHCs, and quantitative microphotometric succinate dehydrogenase (SDH) and glycerol-3-phosphate dehydrogenase (GPDH) enzyme assays. Overload shifted MHC expression in the order IIb --> IIx --> IIa --> alpha/I, with a tripling of cells coexpressing I and alpha-MHC, and a transient reexpression of two embryonic MHC and the neonatal isoform in preexisting myofibers. Overload caused a rapid, size-independent, 50% decrease in GPDH activity across all cell types, which recovered by 6 wk. Fiber SDH activities varied according to MHC composition, such that overloaded fibers coexpressing IIa MHC displayed control slow fiber SDH levels, whereas cells expressing IIx and IIb MHC displayed a transient 30% increase in SDH that recovered by 6 wk. Our results suggest that during overload, fibers adapt progressively to the new functional requirements and display more efficient cellular energy utilization and delivery characteristics. The time course of adaptations suggests a role for glycolytic enzymes in the initiation of these transformations.