NEUTRAL AMINO ACID TRANSPORT IN VASCULAR ENDOTHELIAL CELLS

拟议的研究计划侧重于中性氨基酸在体内的转运。 血管内皮细胞；运输机制和调节方式。 这一提议源于我们的观察，至少有六条不同的路线 在培养的内皮细胞中存在中性氨基酸转运 来自牛的大动脉。在被血清阻止生长的细胞中 去除后，这些运输途径的活性显著增强 血清添加。这表明中性氨基酸在 内皮细胞的生长和增殖。然而，初步数据显示 四种氨基酸，通常是这些运输的典型底物 系统(即系统ASC的丙氨酸、系统A的MeAIB、系统A的谷氨酰胺 系统N和亮氨酸对于系统L)，表示实质上重叠 存在于这些载体系统之间的底物传输中。因此， 需要确定选择性模型底物，以便详细 可以对传输机制进行表征。《缺席》 模型底物的存在排除了对可能的作用机制的解释 血清对氨基酸转运的调节。 具体目标包括：1)表征细胞机制 参与血管内皮细胞的中性氨基酸转运 从牛主动脉衍生，使用选择性模型底物衍生 来自动力学研究和竞赛实验；2)评估 血清对氨基酸转运的促进作用；3)研究 Na~+/H~+交换活化、pH变化与时间的关系 血清促进氨基酸摄取；4)评估可能的第二次 信使系统参与氨基酸转运的调节 血清和5)为研究生提供接触 一系列涉及膜运输及其生化的研究， 生理和药理学方面。 这些研究应该提供有关中性的机制的新信息 血管内皮细胞的氨基酸转运及其可能机制 监管模式(S)。此外，这些研究可能会提供新的见解 氨基酸转运在内皮细胞调控中的作用 生长和扩散。后者似乎是关键，因为有一个 更好地理解血管生成。

The proposed research plan focuses on neutral amino acid transport in vascular endothelial cells; transport mechanisms and modes of regulation. This proposal stems from our observation that at least six different routes for neutral amino acid transport are present in cultured endothelial cells from bovine aorta. In cells which have been growth arrested by serum removal, the activity of these transport pathways are markedly enhanced by serum addition. this suggests that neutral amino acids have a role in endothelial cell growth and proliferation. However, preliminary data on four amino acids which are usually typical substrates of these transport systems (i.e. alanine for system ASC, MeAIB for system A, glutamine for system N and leucine for system L), indicate that substantial overlapping exists in substrate transport among these carrier systems. Therefore, selective model substrates need to be identified so that a detailed characterization of transport mechanisms can be carried out. The absence of model substrates precludes the elucidation of possible mechanisms of regulation of amino acid transport by serum. Specific aims include: 1) characterization of the cellular mechanisms involved in neutral amino acid transport in vascular endothelial cells derived from the bovine aorta, using selective model substrates derived from kinetic studies and competition experiments; 2) evaluation of the stimulatory effect of serum on amino acid transport; 3) investigation of the temporal relation between Na+/H+ exchange activation, pHi-changes and amino acid uptake enhancement by serum; 4) evaluation of possible second messenger systems involved in the regulation of amino acid transport by serum and 5) to offer graduate students the opportunity to be exposed to a line of research that involves membrane transport and its biochemical, physiological and pharmacological aspects. These studies should provide new information on mechanisms for neutral amino acid transport in vascular endothelial cells and their possible mode(s) of regulation. In addition, these studies may provide new insights into the role of amino acid transport in the control of endothelial cell growth and proliferation. The latter appears to be critical to have a better understanding of angiogenesis.