Roskoski R
Brain Res. 1979 Jan 5;160(1):85-93. doi: 10.1016/0006-8993(79)90602-4.
Reuptake of neuroactive amino acids by high affinity transport systems (Km approximately 10 micrometer) is thought to terminate the action of these substances. Since homoexchange can complicate the interpretation of uptake experiments, it is necessary to demonstrate net inward transport of neuroactive amino acids before uptake can be considered as a likely mechanism for transmitter inactivation. When rat cortical synaptosomes are incubated with 10 micrometer [14C]L-aspartate, net (chemical) and apparent (radioactive) uptake into the synaptosomal fractions are equivalent. Although there is net aspartate uptake into the synaptosome fraction, aspartate exchange can be demonstrated in a variety of conditions. Net uptake exhibits the characteristics of high-affinity transport systems including Na+-and temperature-dependence. Furthermore, KCl (or RbCl)--1 micrometer--are required for net uptake but not radioactive or apparent uptake. LiCl, NH4Cl, CsCl, and choline chloride fail to support net uptake. Ouabain (0.1 micrometer) inhibits net uptake to a greater extent than apparent uptake. Although glutamate inhibits aspartate uptake (and vice versa), the net uptake of the combination is greater than that of each alone. The demonstration of net uptake of aspartate by a high-affinity system is consonant with the idea that this system may play a role in its inactivation in the synaptic region.
高亲和力转运系统（Km约为10微米）对神经活性氨基酸的再摄取被认为可终止这些物质的作用。由于同向交换会使摄取实验的解释变得复杂，因此在将摄取视为递质失活的一种可能机制之前，有必要证明神经活性氨基酸的净内向转运。当大鼠皮质突触体与10微米的[14C]L-天冬氨酸一起孵育时，进入突触体组分的净（化学）摄取和表观（放射性）摄取是相等的。尽管存在天冬氨酸向突触体组分的净摄取，但在各种条件下都可证明天冬氨酸的交换。净摄取表现出高亲和力转运系统的特征，包括对Na+和温度的依赖性。此外，净摄取需要1微米的KCl（或RbCl），但放射性摄取或表观摄取则不需要。LiCl、NH4Cl、CsCl和氯化胆碱不能支持净摄取。哇巴因（0.1微米）对净摄取的抑制作用大于表观摄取。尽管谷氨酸抑制天冬氨酸摄取（反之亦然），但两者组合的净摄取大于各自单独的净摄取。高亲和力系统对天冬氨酸净摄取的证明与该系统可能在突触区域其失活过程中起作用的观点一致。
