Aschenbach W G, Brower G L, Talmadge R J, Dobson J L, Gladden L B
Department of Health and Human Performance, Auburn University, Auburn University College of Veterinary Medicine, Auburn, Alabama 36849, USA.
Am J Physiol Regul Integr Comp Physiol. 2001 Jul;281(1):R176-86. doi: 10.1152/ajpregu.2001.281.1.R176.
This study sought to determine the effect of a myocardial volume overload (MVO) on sarcolemmal (SL) lactate (La(-)) transport and the aerobic profile of skeletal muscle. SL vesicles were obtained from female rats 10 wk after either a MVO was induced by creation of an infrarenal fistula (n = 10), or sham surgeries were performed (n = 11). Influx of (14)C-labeled L(+)-La(-) was measured at various unlabeled La(-) concentrations under zero-trans conditions. La(-) transport kinetics were determined using a Michaelis-Menten equation with an added linear component to discriminate between carrier-mediated and diffusional transport. Although heart and lung weights were significantly increased (P < 0.0001) in the MVO group, left ventricular function was only modestly altered (P < 0.05). A significant reduction in type I myosin heavy chain (MHC) in the soleus and a strong trend (P = 0.06) for a reduced type IIx MHC in the plantaris were observed in MVO rats, but no differences in citrate synthase activity or monocarboxylate transporter proteins (MCT)-1 expression were noted in any muscle. Carrier-mediated La(-) influx into SL vesicles was similar between sham and MVO (K(m) = 12 +/- 1 and 18 +/- 3 mM; apparent V(max) = 772 +/- 99 and 827 +/- 80 nmol. mg(-1). min(-1), respectively). Total influx at 100 mM was lower in MVO, and this was due to a 30% reduction in membrane diffusion. In conclusion, a 10-wk MVO did not alter MCT-mediated La(-) transport or protein expression but was associated with modest changes in myofibrillar proteins and impaired SL diffusive properties.
本研究旨在确定心肌容量超负荷（MVO）对肌膜（SL）乳酸（La⁻）转运及骨骼肌有氧代谢状况的影响。从雌性大鼠获取SL囊泡，这些大鼠在通过创建肾下瘘诱导MVO（n = 10）或进行假手术（n = 11）10周后。在零转运条件下，于不同未标记La⁻浓度下测量¹⁴C标记的L⁺-La⁻的流入量。使用米氏方程并添加线性成分来确定La⁻转运动力学，以区分载体介导的转运和扩散转运。尽管MVO组的心脏和肺重量显著增加（P < 0.0001），但左心室功能仅发生适度改变（P < 0.05）。在MVO大鼠中，观察到比目鱼肌中I型肌球蛋白重链（MHC）显著减少，以及跖肌中IIx MHC有降低的强烈趋势（P = 0.06），但在任何肌肉中均未发现柠檬酸合酶活性或单羧酸转运蛋白（MCT）-1表达存在差异。假手术组和MVO组之间，载体介导的La⁻流入SL囊泡的情况相似（米氏常数Kₘ分别为12 ± 1和18 ± 3 mM；表观最大反应速度Vₘₐₓ分别为772 ± 99和827 ± 80 nmol·mg⁻¹·min⁻¹）。在100 mM时，MVO组的总流入量较低，这是由于膜扩散减少了30%。总之，10周的MVO并未改变MCT介导的La⁻转运或蛋白表达，但与肌原纤维蛋白的适度变化及肌膜扩散特性受损有关。
