Naeslund G, Lindqvist I, Ronquist G, Nilson B O
Acta Physiol Scand. 1979 Sep;107(1):57-61. doi: 10.1111/j.1748-1716.1979.tb06442.x.
Blastocysts recovered from mice in a state of delay of implantation were incubated for 10 h with either alpha-aminoisobuturic acid (AIB) or 2,4-diaminobuturic acid (DAB), two non-metabolizable amino acids. The incubation medium was composed so as to maintain growth arrest of the inactive, delayed blastocysts in vitro. The blastocysts were then transferred to a complete outgrowth medium without the two non-metabolizable amino acids to test the capacity for trophoblast outgrowth. AIB, which displays saturation kinetics, was harmless to the blastocysts even at a high concentration, while DAB at a low concentration irreversibly damaged the trophoblast cells and prevented outgrowth, probably due to nonsaturation kinetics resulting in a high intracellular accumulation. The harmful effect of DAB could be abolished by concomitant incubation with L-alanine and L-methionine, which compete with DAB for the same transport system, while the D-forms of the same amino acids had little or no effect. The results suggest the presence of transport System A in mouse blastocysts growth arrested in vitro, indicating an operative carrier mechanism already during delay of implantation.
从处于着床延迟状态的小鼠体内回收的囊胚，用两种不可代谢氨基酸——α-氨基异丁酸（AIB）或2,4-二氨基丁酸（DAB）孵育10小时。孵育培养基的成分设计旨在维持体外处于静止、延迟状态的囊胚的生长停滞。然后将囊胚转移到不含这两种不可代谢氨基酸的完全生长培养基中，以测试滋养层生长能力。表现出饱和动力学的AIB即使在高浓度下对囊胚也无害，而低浓度的DAB会不可逆地损伤滋养层细胞并阻止其生长，这可能是由于非饱和动力学导致细胞内高积累所致。DAB的有害作用可通过与L-丙氨酸和L-甲硫氨酸共同孵育来消除，这两种氨基酸与DAB竞争相同的转运系统，而相同氨基酸的D型几乎没有影响或没有影响。结果表明，在体外生长停滞的小鼠囊胚中存在转运系统A，这表明在着床延迟期间已经存在一种有效的载体机制。
