Sugahara K, Voelker D R, Mason R J
Am Rev Respir Dis. 1987 Mar;135(3):617-21. doi: 10.1164/arrd.1987.135.3.617.
The present experiments were designed to investigate the effect of insulin on amino acid transport by alveolar type II epithelial cells isolated from adult rats. The initial rates of amino acid transport were determined by measuring the uptake of the nonmetabolizable amino acid, alpha-aminoisobutyric acid (AIB). Alveolar type II epithelial cells transported AIB by a sodium-dependent process that displayed saturable kinetics. Insulin stimulated transport of 0.1 mM AIB (82.3 +/- 15.0%, mean +/- SE, n = 4) with a half-maximally effective insulin concentration of 2.2 +/- 1.0 ng/ml (mean +/- SE), which is within the physiologic range of rat serum insulin concentration. Kinetic analysis of AIB transport showed that insulin increased the Vmax from 6.7 +/- 1.2 nmol/10(6) cells/min to 9.3 +/- 1.8 nmol/10(6) cells/min and had no effect on the Km value (5.2 +/- 0.8 mM). Alpha-(methylamino) isobutyric acid, a specific substrate for amino acid transport system A, inhibited both the sodium-dependent and insulin-modulated transport of AIB. Thus, alveolar type II epithelial cells transport amino acids in a sodium-dependent process and insulin stimulates this transport. The present study indicates that insulin may play a physiologic role in regulating amino acid transport in alveolar type II epithelial cells.
本实验旨在研究胰岛素对从成年大鼠分离的Ⅱ型肺泡上皮细胞氨基酸转运的影响。氨基酸转运的初始速率通过测量不可代谢氨基酸α-氨基异丁酸（AIB）的摄取来确定。Ⅱ型肺泡上皮细胞通过一种显示出饱和动力学的钠依赖性过程转运AIB。胰岛素刺激0.1 mM AIB的转运（82.3±15.0%，平均值±标准误，n = 4），半数有效胰岛素浓度为2.2±1.0 ng/ml（平均值±标准误），这在大鼠血清胰岛素浓度的生理范围内。对AIB转运的动力学分析表明，胰岛素将Vmax从6.7±1.2 nmol/10⁶细胞/分钟增加到9.3±1.8 nmol/10⁶细胞/分钟，而对Km值（5.2±0.8 mM）没有影响。氨基酸转运系统A的特异性底物α-（甲氨基）异丁酸抑制了AIB的钠依赖性转运和胰岛素调节的转运。因此，Ⅱ型肺泡上皮细胞通过钠依赖性过程转运氨基酸，胰岛素刺激这种转运。本研究表明胰岛素可能在调节Ⅱ型肺泡上皮细胞的氨基酸转运中发挥生理作用。
