Basova N A, Kushak R I
Fiziol Zh SSSR Im I M Sechenova. 1986 Jun;72(6):810-7.
Presence of two mechanisms in the accumulation of L-tryptophan by the mucosal cells of chicken small intestine was determined in vitro: sodium-independent and sodium-dependent those, the latter being of a major importance. Analysis of the accumulation kinetics in the linear stage showed that at the replacement of sodium with potassium ions in the incubation medium, a decrease of Kt (from 4.44 mM to 1.05 mM) as well as V (from 0.78 mM/min/cm to 0.12 mM/min/cm) occurs. High level of L-threonine, L-alpha-alanine, L-valine (100 mM) considerably inhibit the accumulation of L-tryptophan from 0.24 or 2.40 mM solution, the highest inhibition (78-96%) being related to the sodium-dependent transport mechanism. No considerable changes in Kt (4.0 mM) were observed in the saturated stage of transport whereas V showed a rapid decrease (0.22 mM/min/cm). Adding of modifier 0.64 mM L-alpha-alanine was followed by the increase both in Kt (5.71 mM) and V (0.37 mM/min/cm).
通过体外实验确定了鸡小肠黏膜细胞积累L-色氨酸的两种机制：不依赖钠的机制和依赖钠的机制，后者更为重要。对线性阶段积累动力学的分析表明，在孵育培养基中用钾离子替代钠离子时，Kt（从4.44 mM降至1.05 mM）以及V（从0.78 mM/min/cm降至0.12 mM/min/cm）都会降低。高浓度的L-苏氨酸、L-α-丙氨酸、L-缬氨酸（100 mM）会显著抑制从0.24 mM或2.40 mM溶液中积累L-色氨酸，其中最高抑制率（78 - 96%）与依赖钠的转运机制有关。在转运的饱和阶段未观察到Kt（4.0 mM）有显著变化，而V则迅速下降（0.22 mM/min/cm）。添加0.64 mM L-α-丙氨酸修饰剂后，Kt（5.71 mM）和V（0.37 mM/min/cm）均增加。
