Istituto di Patologia Generale, Università degli Studi di Parma, Via Gramsci 14, I-43100, Parma, Italy.
Amino Acids. 1996 Jun;11(2):117-33. doi: 10.1007/BF00813856.
The functional aspects of sodium dependent amino acid transport in mesenchymal cells are the subject of this contribution. In a survey of the cross-talk existing among the various transport mechanisms, particular attention is devoted to the role played by substrates shared by several transport systems, such as L-glutamine. Intracellular levels of glutamine are determined by the activity of System A, the main transducer of ion gradients built on by Na,K-ATPase into neutral amino acid gradients. Changes in the activity of the System are employed to regulate intracellular amino acid pool and, hence, cell volume. System A activity has been found increased in hypertonically shrunken cells and in proliferating cells. Under both these conditions cells have to increase their volume; therefore, System A can be employed as a convenient mechanism to increase cell volume both under hypertonic and isotonic conditions. Although less well characterized, the uptake of anionic amino acids performed by System X(-) AG may be involved in the maintenance of intracellular amino acid pool under conditions of limited availability of neutral amino acids substrates of System A.
本文主要探讨间质细胞中钠依赖性氨基酸转运的功能方面。在考察各种转运机制之间存在的串扰时，特别关注了几种转运系统共享的底物（如 L-谷氨酰胺）所起的作用。细胞内谷氨酰胺的水平取决于系统 A 的活性，系统 A 是由 Na+，K+-ATPase 构建的离子梯度转化为中性氨基酸梯度的主要转换器。系统的活性变化被用来调节细胞内氨基酸库，从而调节细胞体积。在高渗收缩的细胞和增殖的细胞中发现系统 A 的活性增加。在这两种情况下，细胞都必须增加其体积；因此，系统 A 可以作为一种方便的机制，在高渗和等渗条件下增加细胞体积。尽管系统 X(-)AG 对阴离子氨基酸的摄取特征描述较少，但在中性氨基酸底物（系统 A 的底物）有限的情况下，该摄取可能参与维持细胞内氨基酸库。
