A MODEL OF HIGH AFFINITY GLUTAMIC ACID TRANSPORT BY CORTICAL SYNAPTOSOMES FROM THE LONG‐EVANS RAT
A MODEL OF HIGH AFFINITY GLUTAMIC ACID TRANSPORT BY CORTICAL SYNAPTOSOMES FROM THE LONG‐EVANS RAT
复制标题
长埃文斯大鼠皮质突触体高亲和力谷氨酸转运模型
DOI：
--
复制
发表时间：
1978
影响因子：
4.7
通讯作者：
R. Hollingsworth
中科院分区：
文献类型：
--
作者：
D. Wheeler;R. Hollingsworth
本文测量了Long-Evans大鼠皮质突触小体摄取L-谷氨酸的初始速度随钠和谷氨酸浓度的变化。然后将这些数据拟合到几个可能的模型中的每个模型的速率方程中，并给出最小误差识别的模型。最佳拟合模型的主要预测结果如下：(1)与载体的结合顺序为钠、钠、谷氨酸。(2)摄取应100%依赖于孵育液中钠的存在。(3)在有限的钠浓度下，VMX应该与钠浓度无关，这意味着载体在膜上的转移与钠浓度无关。(4)Lineweaver-Burk样地应与钠浓度的斜率呈线性关系。(5)每个谷氨酸分子应该有两个钠离子的共转运。(6)K_t_1与钠浓度的关系应为：K_t=A/[Na]_2+8/[Na]+C，其中A、B、C为常数。这一结果与之前报道的关于Spraogue-Dawley大鼠的结果有很大不同。Kt，比Sprfague-Dawley大鼠小2-5倍，钠与Kt的关系基本不同。我们还发现耦合比为2，而以前的研究发现耦合比为1。因此，这些结果提出了这样一种可能性，即在钠参与氨基酸运输的机制方面，SpragueDawley和Long-Evans大鼠之间存在根本的差异。
Abstract— The initial velocity of uptake of L‐glutamic acid by cortical synaptosomes from the Long‐Evans rat has been measured as a function of sodium and glutamic acid concentration. These data were then fitted to the rate equation from each of several possible models, and the model giving minimum error identified. The major predictions from the best fit model are as follows: (1) The order of combination with the carrier should be sodium, sodium, glutamic acid. (2) Uptake should be 100% dependent on the presence of sodium in the incubation medium. (3) At a finite concentration of sodium, Vmx should be independent of the sodium concentration, which implies that translocation of the carrier across the membrane is independent of the sodium concentration. (4) Lineweaver‐Burk plots should be linear with slopes depending on the sodium Concentration. (5) There should be co‐transport of two sodium ions with each glutamic acid molecule. (6) The dependence of Kt, on the sodium concentration should have the following form: Kt= A/[Na]2+ 8/[Na] +C, where A, B, and C are constants. The results differ substantially from those previously reported for Sprague‐Dawley rats. Kt, is 2–5 times less than that for Sprfague‐Dawley rats, and the relation of sodium to Kt, is basically different. We also find a coupling ratio of two, whereas previous studies found a coupling ratio of one. Thus the results raise the possibility that there are fundamental differences between Sprague‐Dawley and Long‐Evans rats with regard to the mechanism by which sodium participates in amino acid transport.