Dubouchaud H, Granier P, Mercier J, Le Peuch C, Prefaut C
Laboratoire de Physiologie des Interactions, Service d'Exploration de la Fonction Respiratoire, Hopital Arnaud de Villeneuve, Montpellier, France.
J Appl Physiol (1985). 1996 Feb;80(2):416-21. doi: 10.1152/jappl.1996.80.2.416.
We investigated the effects of 4 wk of hypodynamia on the rate of lactate transport in skeletal muscle sarcolemmal vesicles from control and hindlimb-suspended rats. Characterization of the sarcolemmal preparations was achieved with a marker enzyme (K+-p-nitrophenylphosphatase) and measurement of 1 mM [U-14C]lactate transport activity under zero-trans conditions with or without a pH gradient or the transport inhibitor alpha-hydroxycinnamate. Preparations from the two groups were not significantly different concerning yield and purification. Based on these results, we used this model to analyze the lactate transport activity after hypodynamia by tail suspension. Hindlimb suspension caused a shift from slow to fast myosin heavy chain isoforms in soleus muscles with a 40% decrease in the citrate synthase activity (from 35.3 +/- 3.7 to 21.4 +/- 2.1 mu mol x g-1 x min-1; P < 0.05). Lactate (1 mM) uptake in vesicles from the two groups was a function of time, and the rate after hindlimb suspension was significantly decreased in the suspended compared with the control group (2.25 +/- 0.44 and 3.50 +/- 0.26 nmol x min-1 x mg protein-1, respectively; P < 0.05). These differences were not observed for a higher lactate concentration (50 mM). These results suggest that the level of physical activity plays a role in the regulation of sarcolemmal lactate transport activity implicated in the exchanges of lactate between producing and utilizing cells, organs, and tissues, which are major ways of carbohydrate energy distribution in humans and others species.
我们研究了4周动力减退对对照大鼠和后肢悬吊大鼠骨骼肌肌膜囊泡中乳酸转运速率的影响。通过标记酶（K⁺-对硝基苯磷酸酶）以及在零转运条件下、有或无pH梯度或转运抑制剂α-羟基肉桂酸存在时测量1 mM [U-¹⁴C]乳酸转运活性，对肌膜制剂进行了表征。两组制剂在产量和纯化方面无显著差异。基于这些结果，我们使用该模型分析后肢悬吊致动力减退后的乳酸转运活性。后肢悬吊导致比目鱼肌中肌球蛋白重链同工型从慢速向快速转变，柠檬酸合酶活性降低40%（从35.3±3.7降至21.4±2.1 μmol·g⁻¹·min⁻¹；P<0.05）。两组囊泡对乳酸（1 mM）的摄取是时间的函数，与对照组相比，后肢悬吊组的摄取速率显著降低（分别为2.25±0.44和3.50±0.26 nmol·min⁻¹·mg蛋白⁻¹；P<0.05）。在较高乳酸浓度（50 mM）下未观察到这些差异。这些结果表明，身体活动水平在肌膜乳酸转运活性的调节中起作用，而肌膜乳酸转运活性与产生和利用乳酸的细胞、器官及组织之间的乳酸交换有关，这是人类和其他物种碳水化合物能量分配的主要方式。
