Ye J M, Steen J T, Matthias A, Clark M G, Colquhoun E Q
Division of Biochemistry, University of Tasmania, Hobart, Australia.
Acta Physiol Scand. 1998 May;163(1):49-57. doi: 10.1046/j.1365-201x.1998.00338.x.
Skeletal muscle can release or take up lactate depending on the lactate concentration gradient across the cell membrane. In the perfused rat hindlimb without arterial lactate, both noradrenaline (NA) infusion and increased flow promote lactate release and oxygen consumption (VO2). However, it is unclear whether NA or increased flow rate have similar effects on lactate uptake. The present study compares these effects in the rat hindlimb perfused at a basal flow rate of 0.33 mL min-1 g-1 and 25 degrees C in the presence of added arterial lactate. When 10 mmol L-1 L-(+)-lactate was added to the arterial perfusate, lactate was taken up (16 +/- 1.0 mumol g-1 h-1, n = 13) by the hindlimb with a 35% higher VO2 than that without added lactate. Doubling perfusion flow rate enhanced lactate uptake and VO2 by 120% and 40%, respectively. Glucose uptake was also increased (by 253%) with increased flow. Infusion of NA increased perfusion pressure, VO2 and glucose uptake similarly to those induced by increased flow rate. However, lactate uptake was inhibited by NA. This inhibition was not altered by the beta-adrenergic antagonist propranolol. Vasopressin also showed similar effects to NA to decrease lactate uptake associated with increased VO2 and vasoconstriction. These data indicate that in the presence of a high arterial lactate concentration, NA has opposite effects from increased flow rate on skeletal muscle lactate uptake although both have similar effects on lactate release in the absence of arterial lactate. Inhibition of lactate uptake may relate to the vasoconstrictive action of NA.
骨骼肌可根据细胞膜两侧的乳酸浓度梯度释放或摄取乳酸。在没有动脉血乳酸的灌注大鼠后肢中，去甲肾上腺素（NA）输注和血流量增加均会促进乳酸释放和氧消耗（VO₂）。然而，尚不清楚NA或血流量增加对乳酸摄取是否有类似影响。本研究比较了在基础流速为0.33 mL min⁻¹ g⁻¹且温度为25℃、存在动脉血乳酸的情况下，NA和增加流速对大鼠后肢的这些影响。当向动脉灌注液中添加10 mmol L⁻¹ L-(+)-乳酸时，后肢摄取乳酸（16±1.0 μmol g⁻¹ h⁻¹，n = 13），且VO₂比未添加乳酸时高35%。灌注流速加倍分别使乳酸摄取和VO₂提高了120%和40%。随着流速增加，葡萄糖摄取也增加了（增加了253%）。输注NA使灌注压、VO₂和葡萄糖摄取的增加与流速增加时相似。然而，NA抑制了乳酸摄取。β-肾上腺素能拮抗剂普萘洛尔并未改变这种抑制作用。血管加压素对降低乳酸摄取也显示出与NA类似的作用，同时伴有VO₂增加和血管收缩。这些数据表明，在动脉血乳酸浓度较高时，NA对骨骼肌乳酸摄取的影响与流速增加相反，尽管在没有动脉血乳酸时两者对乳酸释放有类似影响。乳酸摄取的抑制可能与NA的血管收缩作用有关。
