Retinoids (vitamin A and its derivatives) play an essential role in many biological functions. However mammals are incapable of de novo synthesis of vitamin A and must acquire it from the diet. In the intestine, dietary retinoids are incorporated in chylomicrons as retinyl esters, along with other dietary lipids. The majority of dietary retinoid is cleared by and stored within the liver. To meet vitamin A requirements of tissues, the liver secretes retinol (vitamin A alcohol) into the circulation bound to its sole specific carrier protein, retinol-binding protein (RBP). The single known function of this protein is to transport retinol from the hepatic stores to target tissues. Over the last few years, the generation of knockout and transgenic mouse models has significantly contributed to our understanding of RBP function in the metabolism of vitamin A. We discuss below the role of RBP in maintaining normal vision and a steady flux of retinol throughout the body in times of need.

中文翻译：

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使用转基因和基因剔除小鼠模型了解视黄醇结合蛋白在维生素A代谢中的生理作用。

类维生素A（维生素A及其衍生物）在许多生物学功能中起着至关重要的作用。然而，哺乳动物不能从头合成维生素A，必须从饮食中获取。在肠道中，饮食类维生素A与其他饮食类脂质一起以视黄基酯的形式掺入乳糜微粒中。饮食中的大多数类维生素A被肝脏清除并储存在肝脏中。为了满足组织对维生素A的需求，肝脏在循环系统中将视黄醇（维生素A醇）分泌到与其唯一的特异性载体蛋白视黄醇结合蛋白（RBP）结合。该蛋白的单一已知功能是将视黄醇从肝存储转运到靶组织。在过去几年间，