Lai M M, Booth F W
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225.
J Appl Physiol (1985). 1990 Sep;69(3):843-8. doi: 10.1152/jappl.1990.69.3.843.
A diet of 1% beta-guanidinopropionic acid (beta-GPA) fed to rats for weeks results in decreased muscle adenosine triphosphate and creatine phosphate concentrations (J. Biol. Chem. 249: 1060-1063, 1974), increased activities of selected mitochondrial enzymes (Biochem. J. 232: 125-131, 1985), and atrophied type IIb fibers (Lab. Invest. 33: 151-158, 1975). The hypothesis of the present study was that chronic beta-GPA feeding would increase cytochrome c mRNA in muscle and would decrease alpha-skeletal actin mRNA in type IIb muscle. Data collected supported, in part, the hypothesis. After 22 days of a 1% beta-GPA diet, cytochrome c mRNA was increased 60-67% in muscles with inherently low cytochrome c mRNA but was not altered in muscles with higher cytochrome c mRNA levels. alpha-Skeletal actin mRNA was unchanged in muscles with low and high cytochrome c mRNA after 22 days of 1% beta-GPA. After 66 days of beta-GPA feeding, both cytochrome c mRNA and alpha-skeletal actin mRNA were decreased 18 and 26%, respectively, per unit of total RNA, in white quadriceps muscle. At the same time muscles composed of predominantly type II fibers atrophied 22%, whereas type I muscle size was unaltered. These data suggest that high-energy phosphate levels could play some role in adaptive changes in muscle composition.
给大鼠喂食含1%β-胍基丙酸（β-GPA）的日粮数周，会导致肌肉中三磷酸腺苷和磷酸肌酸浓度降低（《生物化学杂志》249: 1060 - 1063, 1974），某些线粒体酶的活性增加（《生物化学杂志》232: 125 - 131, 1985），以及IIb型纤维萎缩（《实验医学杂志》33: 151 - 158, 1975）。本研究的假设是，长期喂食β-GPA会增加肌肉中细胞色素c的信使核糖核酸（mRNA），并降低IIb型肌肉中α-骨骼肌动蛋白的mRNA。收集到的数据部分支持了这一假设。在含1%β-GPA的日粮喂养22天后，细胞色素c mRNA在原本细胞色素c mRNA水平较低的肌肉中增加了60 - 67%，但在细胞色素c mRNA水平较高的肌肉中没有变化。在1%β-GPA喂养22天后，低水平和高水平细胞色素c mRNA的肌肉中，α-骨骼肌动蛋白mRNA均未改变。在β-GPA喂养66天后，白色股四头肌中每单位总RNA的细胞色素c mRNA和α-骨骼肌动蛋白mRNA分别下降了18%和26%。与此同时，主要由II型纤维组成的肌肉萎缩了22%，而I型肌肉大小未改变。这些数据表明，高能磷酸水平可能在肌肉组成的适应性变化中发挥一定作用。
