Rhoades R A, Shaw M E, Eskew M L, Wali S
Am J Physiol. 1978 Dec;235(6):E619-23. doi: 10.1152/ajpendo.1978.235.6.E619.
Glucose utilization and lactate metabolism were studied in isolated rat lungs perfused with a Krebs-Henseleit bicarbonate buffer, pH 7.4, containing either [U-14C]lactate, [U-14C]glucose, or [U-14C]alanine. Glucose uptake showed an apparent Km of 4.7 mM and a Vmax of 107 mumol-g dry wt-1-h-1. Lactate production under these conditions showed a Vmax of 82.9 mumol-g dry wt-1-h-1. At high circulating lactate level (7 mM), the perfused lung showed an increased capacity to utilize [U-14C]lactate with preferential incorporation into lung lipids. At equal molar concentration (5 mM) [U-14C]lactate was preferentially incorporated over [U-14C]glucose. Addition of 5 mM lactate to the perfusion medium did not affect lactate production. Perfused lungs from fasted rats showed higher lactate production, with increased amounts of [U-14C]alanine converted to lactate by the perfused lung, indicating lactate can also be derived from noncarbohydrate sources. These data show that under aerobic conditions the perfused lung can produce and utilize lactate simultaneously, and lactate can serve as a potential substrate for lung lipids.
在灌注有pH 7.4的Krebs-Henseleit碳酸氢盐缓冲液的离体大鼠肺中研究了葡萄糖利用和乳酸代谢，该缓冲液含有[U-14C]乳酸、[U-14C]葡萄糖或[U-14C]丙氨酸。葡萄糖摄取的表观Km为4.7 mM，Vmax为107 μmol·g干重-1·h-1。在这些条件下乳酸生成的Vmax为82.9 μmol·g干重-1·h-1。在高循环乳酸水平（7 mM）时，灌注肺利用[U-14C]乳酸的能力增强，且优先将其掺入肺脂质中。在等摩尔浓度（5 mM）下，[U-14C]乳酸比[U-14C]葡萄糖更优先被掺入。向灌注培养基中添加5 mM乳酸不影响乳酸生成。禁食大鼠的灌注肺显示出更高的乳酸生成，灌注肺将更多的[U-14C]丙氨酸转化为乳酸，这表明乳酸也可来源于非碳水化合物来源。这些数据表明，在有氧条件下，灌注肺可同时产生和利用乳酸，且乳酸可作为肺脂质的潜在底物。
