VITAMIN A TRANSPORT SYSTEMS

这个项目的长期目标是研究哪些因素 影响维生素A运输系统的调节， （一）实现这一目标的机制。 的 特别感兴趣的是拟议期间的具体 结合蛋白和特定的酶是必要的， 维生素A的吸收过程。 其中包括Cellular 视黄醇结合蛋白2型（CRBP（II）），存在于小 肠和细胞视黄醇结合蛋白（CRBP），存在于 肝脏 肠道中的酶是胡萝卜素- 裂解酶、微粒体视黄醇还原酶和微粒体 卵磷脂视黄醇酰基转移酶 一种类似的分解酶是 存在于肝脏中。 拟议的工作将审查这些约束力是否 蛋白质和酶的活性是协调调节， 以确保维生素A的有效吸收。 在 大鼠，可能的协调调节将被检查1）沿沿着 水平（空肠-回肠）和垂直（隐窝-绒毛）轴 成熟小肠; 2）在肠道发育过程中， 肝脏; 3）妊娠期和哺乳期; 4）适应期 小肠切除术后发生的小肠，或 换位;和5）在不同的摄入量的影响下， 维生素A，如β-胡萝卜素或视黄酯。 尤其是在肝脏中， 注意到一种新的酯合酶，卵磷脂视黄醇酰基 将其纯化。 特异性抗血清将 通过RIA和免疫组织化学检测， 实质细胞和星状细胞的细胞特异性调节 肝脏在发育过程中和不同的维生素A摄入量。 人CRBP（II）将被纯化并用于定义维生素A 人体吸收系统。 将特别注意 非常早产的婴儿，以确定是否必要的元素， 维生素A的有效吸收。

The long-term goals of this project are to examine what factors affect the regulation of the vitamin A transport systems and the mechanism(s) by which such regulation is accomplished. Of particular interest for the proposed period are the specific binding proteins and specific enzymes that are necessary for the overall process of absorption of vitamin A. These include cellular retinol-binding protein, type two, (CRBP(II)), present in the small intestine and cellular retinol-binding protein (CRBP), present in the liver. The enzymes in the gut of interest are the carotene- cleavage enzyme, a microsomal retinal-reductase, and a microsomal lecithinretinol acyl transferase. A similar esterifying enzyme is present in liver. The work proposed will examine if these binding proteins and enzyme activities are coordinately regulated in both rat and human to ensure the efficient absorption of vitamin A. In rat, possible coordinate regulation will be examined 1) along the horizontal (duodenumjejunum-ileum) and vertical (crypt-villus) axes of the mature small intestine; 2) during development of the gut and liver; 3) during pregnancy and lactation; 4) during the adaptation of the small intestine that occurs after surgical resection or transposition; and 5) under the influence of varying intakes of vitamin A, as beta-carotene or retinyl ester. In liver, particular attention is given to a new ester synthase, lecithinretinol acyl transferase, which will be purified. Specific antiserum will be produced to examine, by RIA and immunohistochemistry, its possible cell-specific regulation in the parenchymal and stellate cells of the liver during development and with varying intake of vitamin A. Human CRBP(II) will be purified and used to define the vitamin A absorptive system in human. Particular attention will be given to the very premature infant to determine if the elements necessary for efficient absorption of vitamin A are being expressed.