Torgan C E, Brozinick J T, Kastello G M, Ivy J L
Department of Kinesiology, University of Texas at Austin 78712.
J Appl Physiol (1985). 1989 Nov;67(5):1807-13. doi: 10.1152/jappl.1989.67.5.1807.
The purposes of the present study were to characterize the histochemical and enzymatic profiles of various hindlimb skeletal muscles, as well as to determine maximal O2 consumption (VO2max) and respiratory exchange ratios (R) during steady-state exercise in the obese Zucker rat. The changes that occurred in these parameters in response to a 6-wk training program were then assessed. Obese rats were randomly assigned to a sedentary or training group. Lean littermates served as a second control. Training consisted of treadmill running at 18 m/min up an 8% grade, 1.5 h/day, 5 day/wk for 6 wk. During week 6, VO2max and R during a steady-state run (74% max) were determined. After 2 days of inactivity, hindlimb muscles were excised, stained for fiber type and capillaries, and assayed for hexokinase, citrate synthase, cytochrome oxidase, and beta-hydroxyacetyl-CoA dehydrogenase. The obese sedentary rats demonstrated greater oxidative enzyme activities per gram of muscle tissue than their lean littermates, greater R values during submaximal exercise of the same relative intensity, and greater absolute VO2max values. Training resulted in a 20-56% increase in oxidative enzymes, a 10% increase in VO2max, and an increase in capillary density in the soleus and plantaris. There was no alteration in R values during exercise at 74% VO2max or in fiber type composition in response to exercise training. Results suggest that the muscle of the obese Zucker rat manifests a greater oxidative capacity than the muscle of its lean littermates. The apparent inability of the obese rat to increase its use of fat during submaximal exercise of the same relative intensity in response to training remains to be elucidated.
本研究的目的是描述各种后肢骨骼肌的组织化学和酶学特征，以及测定肥胖Zucker大鼠在稳态运动期间的最大耗氧量（VO2max）和呼吸交换率（R）。然后评估这些参数在为期6周的训练计划后的变化。肥胖大鼠被随机分为久坐组或训练组。瘦的同窝大鼠作为第二个对照组。训练包括在坡度为8%的跑步机上以18米/分钟的速度跑步，每天1.5小时，每周5天，共6周。在第6周期间，测定稳态跑步（最大强度的74%）时的VO2max和R。在不活动2天后，切除后肢肌肉，进行纤维类型和毛细血管染色，并测定己糖激酶、柠檬酸合酶、细胞色素氧化酶和β-羟基乙酰辅酶A脱氢酶。肥胖久坐大鼠每克肌肉组织的氧化酶活性高于其瘦的同窝大鼠，在相同相对强度的次最大运动期间的R值更高，绝对VO2max值也更高。训练导致氧化酶增加20%-56%，VO2max增加10%，比目鱼肌和跖肌的毛细血管密度增加。在74%VO2max的运动期间，R值或运动训练引起的纤维类型组成没有变化。结果表明，肥胖Zucker大鼠的肌肉比其瘦的同窝大鼠的肌肉表现出更大的氧化能力。肥胖大鼠在相同相对强度的次最大运动期间对训练的反应中明显无法增加脂肪的利用，这一点仍有待阐明。
