Malo C
Department of Physiology, Faculty of Medicine, Université de Montréal, Canada.
Biochim Biophys Acta. 1993 Dec 12;1153(2):299-307. doi: 10.1016/0005-2736(93)90419-z.
The kinetic parameters of Na+/D-glucose cotransport were examined in fetal, newborn and adult guinea-pig jejunal brush-border membrane vesicles using a displacement curve and non-linear regression procedure. Our data indicated the presence of a single system with a Km of 0.34 +/- 0.04 mM at both 20 degrees C and 35 degrees C. Vmax was increased by about 4-fold when the kinetic experiments were performed at 35 degrees C. Since our results were not in agreement with the findings of Brot-Laroche et al. (J. Biol. Chem. (1986) 261, 6168-6176) which indicated the existence of a distinct D-glucose transport system in the adult guinea-pig jejunum at 35 degrees C, we verified the influence of their experimental conditions on initial rate uptake measurements. In the presence of D-sorbitol instead of D-mannitol in the transport media, 70% inhibition of D-glucose uptake was observed, an effect which was attributable to contamination of sorbitol preparations by D-glucose. After removal of glucose contamination D-sorbitol did not significantly reduce the initial rate of D-glucose transport. These results led us to conclude the existence of a single D-glucose transport system in the guinea-pig small intestine and to stress the choice of experimental conditions as being crucial for an accurate estimation of kinetic parameters.
利用置换曲线和非线性回归程序，对胎儿、新生和成年豚鼠空肠刷状缘膜囊泡中Na⁺/D -葡萄糖共转运的动力学参数进行了研究。我们的数据表明，在20℃和35℃时均存在一个Km为0.34±0.04 mM的单一系统。当在35℃进行动力学实验时，Vmax增加了约4倍。由于我们的结果与Brot - Laroche等人（《生物化学杂志》（1986年）261, 6168 - 6176）的发现不一致，他们指出在35℃成年豚鼠空肠中存在一个独特的D -葡萄糖转运系统，我们验证了他们的实验条件对初始摄取速率测量的影响。在转运介质中用D -山梨醇代替D -甘露醇时，观察到D -葡萄糖摄取受到70%的抑制，这种效应归因于山梨醇制剂被D -葡萄糖污染。去除葡萄糖污染后，D -山梨醇并没有显著降低D -葡萄糖转运的初始速率。这些结果使我们得出结论，豚鼠小肠中存在一个单一的D -葡萄糖转运系统，并强调实验条件的选择对于准确估计动力学参数至关重要。
