Beaudry M, Duvallet A, Thieulart L, el Abida K, Rieu M
Laboratoire de physiologie des adaptations, CHU Cochin, Paris, France.
Acta Physiol Scand. 1991 Mar;141(3):379-81. doi: 10.1111/j.1748-1716.1991.tb09094.x.
During exercise, lactate is produced by degradation of glucose-6-phosphate during glycolysis in the contracting muscles. This lactate is metabolized during and after exercise in the muscle itself and also in the liver and other muscles, which can use it as an energy metabolite or can resynthetize glycogen. Lactate is transported in the blood, and the rate of muscular utilization may be limited by two factors: the rate of metabolic utilization by the muscle cell; and the rate of transport across the membrane regulating lactate transfer from the blood to the cell. We have studied lactate uptake in L6 muscle cells by incorporation of 14C-lactate. The uptake rates were linear for 20 seconds with 5 mM lactate and 10 seconds with 20 mM. The uptake during 10 seconds for physiological lactate concentrations (1-20 mM) gave a straight line passing through the origin. Lactate uptake was not altered by specific inhibitors of lactate transport (2.5 mM alpha cyano-4-hydroxycinnamic acid. 5 microM 4,4'-diisothiocyanostilbene-2,2'disulphonic acid) or by the stereospecific D-lactate inhibitor. The results suggest that L-lactate uptake in L6 cells occurs by passive diffusion.
运动期间，收缩肌肉中的糖酵解过程中，葡萄糖-6-磷酸降解产生乳酸。在运动期间及运动后，这种乳酸在肌肉自身以及肝脏和其他肌肉中被代谢，这些组织可以将其用作能量代谢物或重新合成糖原。乳酸在血液中运输，肌肉对其的利用速率可能受两个因素限制：肌肉细胞的代谢利用速率；以及调节乳酸从血液转运至细胞的跨膜运输速率。我们通过掺入14C-乳酸研究了L6肌肉细胞对乳酸的摄取。在5 mM乳酸浓度下，摄取速率在20秒内呈线性，在20 mM乳酸浓度下，摄取速率在10秒内呈线性。对于生理乳酸浓度（1 - 20 mM），10秒内的摄取呈一条过原点的直线。乳酸摄取不受乳酸转运特异性抑制剂（2.5 mM α-氰基-4-羟基肉桂酸、5 μM 4,4'-二异硫氰基芪-2,2'-二磺酸）或立体特异性D-乳酸抑制剂的影响。结果表明，L6细胞对L-乳酸的摄取是通过被动扩散进行的。
