Derr J T, Smith G L
J Cell Physiol. 1980 Jan;102(1):55-62. doi: 10.1002/jcp.1041020109.
Enhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication-stimulating activity (MSA). This increase in amino acid transport is an early event occurring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by alpha-aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na+-dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly+ upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while Km remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.
当通过添加纯化的增殖刺激活性（MSA）刺激鸡胚成纤维细胞的静止培养物进行增殖时，可观察到氨基酸转运增强。这种氨基酸转运的增加是刺激细胞中DNA合成开始之前发生的早期事件。结果表明，通过α-氨基异丁酸（AIB）摄取测量的转运活性变化仅归因于对Na +依赖性A转运系统的刺激。暴露于MSA后，ASC、L或Ly +转运系统的活性几乎没有变化。动力学分析表明，这种增加的活性是由于Vmax的变化，而Km保持不变。需要持续暴露于刺激以维持转运活性的增加水平，并且RNA和蛋白质合成抑制剂的存在会显著抑制该反应。结果还表明，当RSV tsNY68感染的细胞转移到允许温度时，A转运系统也会出现类似的特异性增加。似乎A介导系统正在成为细胞功能的一个重要调节位点。
