VITAMIN A TRANSPORT SYSTEMS

该项目的长期目标是检查哪些因素 影响维生素A运输系统的调节和 完成这种监管的机制(S)。的 建议期间的特别利息是指 结合蛋白质和特定的酶是必需的 吸收维生素A的整个过程，包括细胞 视黄醇结合蛋白，第二型，(CRBP(II))，存在于 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，一种微体视网膜还原酶和一种微体 卵磷脂视黄醇酰基转移酶。一种类似的酯化酶是 存在于肝脏中。拟议的工作将检查这些约束性 蛋白质和酶的活性在两者中是协调调节的 确保大鼠和人类对维生素A的有效吸收 大鼠，可能的协调调节将沿着1)检查 水平(十二指肠空肠-回肠)和垂直(隐窝-绒毛)轴 成熟的小肠；2)在肠道的发育和 肝脏；3)孕期和哺乳期；4)适应期 手术切除后或手术后发生的小肠病变 换位；以及5)在不同摄入量的影响下 维生素A，如β-胡萝卜素或视黄酸酯。在肝脏，特别是 关注一种新的酯合成酶，卵磷脂视黄醇酰基 转移酶，将被提纯。特定的抗血清将会是 通过放射免疫分析和免疫组织化学检测其是否可能 松材线虫实质细胞和星状细胞的细胞特异性调控 肝脏在发育过程中，维生素A的摄入量各不相同。 人CRBP(II)将被提纯并用于确定维生素A 人体内的吸收系统。我们将特别注意 以确定早产儿是否有必要的元素 对于维生素A的有效吸收，正在被表达出来。

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.