Baker M E
Department of Medicine, University of California, San Diego, La Jolla 92093-0623, USA.
FEBS Lett. 1998 Nov 13;439(1-2):9-12. doi: 10.1016/s0014-5793(98)01346-5.
Albumin, the major serum protein, binds a wide variety of lipophilic compounds including steroids, other lipophilic hormones and phytochemicals that bind to hormone receptors. Albumin has a low affinity for these lipophilic compounds. However, due to albumin's high concentration in serum, albumin is a major carrier of steroids and lipophilic hormones and regulator of their access to their receptors. Moreover, albumin functions as a sink for phytochemicals, which prevents their binding to hormone receptors and other cellular proteins, protecting animals from disruptive phytochemical-mediated endocrine effects. We propose that these properties of albumin were important in protochordates and vertebrates about 550 to 520 million years ago, just before and during the Cambrian. At that time, animal body sizes and exposure to phytochemicals in food were increasing, and animals in which albumin expression was high had a selective advantage in surviving and reproducing in the presence of toxic phytochemicals. This hypothesis that albumin has essential function(s) in mammalian endocrine physiology can be tested by comparing the effects of phytochemicals in Nagase rats that have 1/1000 the normal albumin concentration or in mice in which the albumin gene is knocked out with those in normal rats and mice.
白蛋白是主要的血清蛋白，它能结合多种亲脂性化合物，包括类固醇、其他亲脂性激素以及与激素受体结合的植物化学物质。白蛋白对这些亲脂性化合物的亲和力较低。然而，由于白蛋白在血清中的浓度较高，它是类固醇和亲脂性激素的主要载体，也是它们与受体结合的调节剂。此外，白蛋白还起到植物化学物质储存库的作用，防止它们与激素受体及其他细胞蛋白结合，保护动物免受植物化学物质介导的内分泌干扰效应的影响。我们推测，大约在5.5亿至5.2亿年前的寒武纪之前及寒武纪期间，白蛋白的这些特性在原索动物和脊椎动物中就已十分重要。那时，动物的体型以及食物中植物化学物质的摄入量都在增加，在有毒植物化学物质存在的情况下，白蛋白表达量高的动物在生存和繁殖方面具有选择优势。可以通过比较植物化学物质对正常白蛋白浓度仅为正常水平千分之一的长濑大鼠或白蛋白基因被敲除的小鼠，与正常大鼠和小鼠的影响，来验证白蛋白在哺乳动物内分泌生理学中具有重要功能这一假说。
