ACTIVATION OF A NA+-DEPENDENT AMINO-ACID TRANSPORT-SYSTEM IN PREIMPLANTATION MOUSE EMBRYOS
ACTIVATION OF A NA+-DEPENDENT AMINO-ACID TRANSPORT-SYSTEM IN PREIMPLANTATION MOUSE EMBRYOS
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DOI：
10.1016/0012-1606(74)90199-7
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发表时间：
1974-01-01
影响因子：
2.7
通讯作者：
TASCA, RJ
中科院分区：
文献类型：
--
作者：
BORLAND, RM;TASCA, RJ
已经研究了从完全确定的培养基中将l-蛋氨酸-甲基-3H和l-亮氨酸-3H摄取到植入前小鼠胚胎的酸溶性级分中。体外培养的晚期四细胞胚胎和早期囊胚可以通过表现出可饱和的米氏动力学（载体介导的主动运输系统的特征）的过程来浓缩两种氨基酸。这种吸收对温度敏感，并受到某些竞争相同吸收位点的氨基酸的抑制。在四细胞阶段，蛋氨酸的摄取似乎是由单一运输系统（Km= 6.25 × 10−5M）介导的。复杂的动力学表明，早期囊胚阶段存在两种不同的运输系统（Km= 6.25 × 10−5M；8.9 × 10−4M）。从四细胞阶段后期到囊胚阶段，蛋氨酸和亮氨酸运输的 Vmax 值（mg/胚胎/15 分钟）显着增加，表明在发育过程中产生或激活了额外的载体。最重要的是，亮氨酸和蛋氨酸运输是在四细胞阶段不依赖Na+，在桑葚阶段蛋氨酸转运部分依赖，并且在胚泡阶段这两种氨基酸完全依赖Na+。累积结果表明，植入前胚胎通过特定的化学介导的主动运输系统积累亮氨酸和蛋氨酸。细胞膜功能的定性和定量发育变化可能代表胚胎和/或滋养层细胞随后生长的准备步骤。
The uptake ofl-methionine-methyl-3H andl-leucine-3H from completely defined medium into acid-soluble fractions of preimplantation mouse embryos has been studied. Late four-cell embryos and early blastocysts raisedin vitrocan concentrate both amino acids by processes which exhibit saturable, Michaelis-Menten type kinetics, characteristic of carrier-mediated active transport systems. This uptake is temperature-sensitive and inhibited by certain amino acids which compete for the same uptake sites. Methionine uptake seems to be mediated by a single transport system (Km= 6.25 × 10−5M) at the four-cell stage. Complex kinetics suggest that two distinct transport systems exist at the early blastocyst stage (Km= 6.25 × 10−5M; 8.9 × 10−4M).Vmaxvalues (mg/embryo/15 min) for methionine and leucine transport increase significantly from the late four-cell stage to the blastocyst stage, suggesting that additional carriers are produced or activated during development.Most importantly, leucine and methionine transport is Na+-independent at the four-cell stage, methionine transport is partially dependent at the morula stage, and both amino acids are completely Na+-dependent at the blastocyst stage. The cumulative results suggest that preimplantation embryos accumulate leucine and methionine by specific, chemically mediated, active transport systems. The qualitative and quantitative developmental changes in cell membrane function may represent preparatory steps for subsequent growth of embryonic and/or trophoblastic cells.