Fitts R H, Brimmer C J, Heywood-Cooksey A, Timmerman R J
Department of Biology, Marquette University, Milwaukee, Wisconsin 53233.
Am J Physiol. 1989 May;256(5 Pt 1):C1082-91. doi: 10.1152/ajpcell.1989.256.5.C1082.
The purpose of this investigation was to determine how models of weightlessness, hindlimb suspension (HS), and hindlimb immobilization (HI) affect the metabolic enzyme profile in the slow oxidative (SO), fast oxidative glycolytic (FOG), and fast glycolytic (FG) fibers of rat hindlimb. After 1, 2, or 4 wk of HS or HI, single fibers were isolated from freeze-dried soleus and gastrocnemius muscles; a small section of each fiber was run on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels to identify fiber type, and the remaining piece was assayed for either lactate dehydrogenase (LDH) and citrate synthase (CS) or phosphofructokinase (PFK) and beta-hydroxyacyl-CoA dehydrogenase (beta-OH-acyl-CoA). Two weeks of HS induced an almost twofold increase in the activity of CS (2.13 +/- 0.13 vs. 3.60 +/- 0.26 mol.kg dry wt-1.h-1) in the SO fiber of the soleus, and the activity stayed high at 4 wk. Although the FOG fiber had significantly higher CS activity (3.85 +/- 0.29) than either the SO or FG (1.59 +/- 0.16 mol.kg dry wt-1.h-1) fiber, neither fast fiber type was altered by HS. The glycolytic enzymes LDH and PFK were both elevated in the SO fiber after HS. The increase in LDH occurred by 1 wk (14.80 +/- 1.51 vs. 8.83 +/- 0.78), whereas the activity of PFK was not significantly changed until 4 wk (1.16 +/- 0.13 vs. 0.68 +/- 0.05 mol.kg dry wt-1.h-1). The control FG fiber had the highest LDH (44.30 +/- 2.29) and PFK (2.40 +/- 0.16) activities, followed by the FOG fiber (LDH, 34.10 +/- 2.83; PFK, 1.62 +/- 0.17 mol.kg dry wt-1.h-1); however, the activities of these glycolytic enzymes in the fast fiber types were unaltered by HS. The activity of beta-OH-acyl-CoA was not affected by HS in either the slow or fast fiber types. HI showed qualitatively similar changes to those observed with HS; however, the enzyme shifts developed with a slower time course. In conclusion, both HS and HI shifted the SO fiber enzyme pattern toward that of the control FOG fiber; however, a complete conversion from the SO to FOG fiber did not occur within the 4-wk treatment period.
本研究的目的是确定失重、后肢悬吊（HS）和后肢固定（HI）模型如何影响大鼠后肢慢氧化（SO）、快氧化糖酵解（FOG）和快糖酵解（FG）纤维中的代谢酶谱。在HS或HI处理1、2或4周后，从冻干的比目鱼肌和腓肠肌中分离出单根纤维；将每根纤维的一小部分进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳，以确定纤维类型，其余部分用于检测乳酸脱氢酶（LDH）和柠檬酸合酶（CS）或磷酸果糖激酶（PFK）和β-羟基酰基辅酶A脱氢酶（β-OH-酰基辅酶A）。两周的HS诱导比目鱼肌SO纤维中CS活性几乎增加了两倍（2.13±0.13对3.60±0.26 mol·kg干重-1·h-1），且在4周时活性仍保持较高水平。尽管FOG纤维的CS活性（3.85±0.29）显著高于SO或FG纤维（1.59±0.16 mol·kg干重-1·h-1），但两种快纤维类型均未因HS而改变。HS后，SO纤维中的糖酵解酶LDH和PFK均升高。LDH的增加在1周时出现（14.80±1.51对8.83±0.78），而PFK的活性直到4周时才显著变化（1.16±0.13对0.68±0.05 mol·kg干重-1·h-1）。对照FG纤维的LDH（44.30±2.29）和PFK（2.40±0.16）活性最高，其次是FOG纤维（LDH，34.10±2.83；PFK，1.62±0.17 mol·kg干重-1·h-1）；然而，这些糖酵解酶在快纤维类型中的活性未因HS而改变。β-OH-酰基辅酶A的活性在慢纤维和快纤维类型中均未受HS影响。HI显示出与HS观察到的定性相似的变化；然而，酶的变化发展时间进程较慢。总之，HS和HI均使SO纤维的酶模式向对照FOG纤维的模式转变；然而，在4周的治疗期内，并未发生从SO纤维到FOG纤维的完全转变。
