Gromova L V, Gruzdkov A A
I. P. Pavlov Institute of Physiology, Russian Acad. Sci., 199034, St. Petersburg, Nab. Makarova, 6, Russia.
Ross Fiziol Zh Im I M Sechenova. 2003 Feb;89(2):173-83.
Kinetics of glycylglycine hydrolysis and absorption as well as that of free glycine absorption in isolated loop of the small intestine was studied in chronic experiments in two groups of rats. In the 1st group (n = 5), the isolated loop daily received for 1 or two hours a glucose load (25 mM), whereas in the 2nd group (n = 4)--a glutamic acid load (25 mM). The "true" values (i.e. corrected for the influence of the pre-epithelial layer) of the Michaelis constant for dipeptide transport were lower than those for the free glycine transport: 16 +/- 1.8 versus 36.3 +/- 3.7 mM (in the 1st group) and 15.9 +/- 2.2 versus 34.0 +/- 3.7 mM (in the 2nd group), whereas values of the maximal rate of active transport as calculated per 1 cm of the intestine length were, on the contrary, higher: 0.64 +/- 0.06 versus 0.42 +/- 0.10 mumol/(min.cm) 1st group and 0.86 +/- 0.13 versus 0.56 +/- 0.04 mumol/(min.cm) in the in the 2nd group. It has been shown that, under these conditions, regarded as the most physiological, over 90% of glycylglycine is absorbed via the peptide transport system. Only a small part of this dipeptide amount (less than 10%) splits during membrane hydrolysis with subsequent absorption of the derived glycine. It has also been found that glutamic acid solution as a regular substrate load is more effective (as compared with the glucose solution) in retarding the atrophic changes occurring in the isolated intestine loop and in preserving its structural and functional parameters on a higher level.
在两组大鼠的慢性实验中，研究了甘氨酰甘氨酸水解与吸收的动力学以及游离甘氨酸在小肠分离肠袢中的吸收动力学。第一组（n = 5），分离肠袢每天接受1或2小时的葡萄糖负荷（25 mM），而第二组（n = 4）接受谷氨酸负荷（25 mM）。二肽转运的米氏常数的“真实”值（即校正了上皮前层的影响）低于游离甘氨酸转运的米氏常数：第一组为16±1.8对36.3±3.7 mM，第二组为15.9±2.2对34.0±3.7 mM，而每厘米肠长度计算的主动转运最大速率值则相反，更高：第一组为0.64±0.06对0.42±0.10 μmol/(min·cm)，第二组为0.86±0.13对0.56±0.04 μmol/(min·cm)。结果表明，在这些被视为最生理的条件下，超过90%的甘氨酰甘氨酸通过肽转运系统吸收。该二肽只有一小部分（不到10%）在膜水解过程中分解，随后衍生的甘氨酸被吸收。还发现，作为常规底物负荷的谷氨酸溶液（与葡萄糖溶液相比）在延缓分离肠袢中发生的萎缩性变化以及将其结构和功能参数维持在更高水平方面更有效。
