Studies of albumin binding to rat liver plasma membranes. Implications for the albumin receptor hypothesis.
Studies of albumin binding to rat liver plasma membranes. Implications for the albumin receptor hypothesis.
复制标题
DOI：
10.1016/0304-4165(83)90019-3
复制
发表时间：
1983-03
期刊：
影响因子：
--
通讯作者：
W. Stremmel;B. Potter;P. Berk
中科院分区：
文献类型：
--
作者：
W. Stremmel;B. Potter;P. Berk
为了表征先前提出的一种肝细胞白蛋白受体，我们检测了天然的和脱脂的125I标记的大鼠白蛋白与大鼠肝脏质膜的结合。孵育30min后，根据初始离心(15000×g，15min)膜微球与上清液之间的放射性分布，反复用缓冲液洗涤和重新离心，确定结合情况。125I标记白蛋白在初始膜微球中的平均回收率仅为孵育的4%。此外，这种白蛋白与膜的结合很松散，三次洗涤后小球中的回收率低于计数的0.5%。~(125)I标记的白蛋白与质膜的结合不大于与红细胞膜的结合，不被过量的未标记白蛋白抑制，也不因膜的热变性而减少，所有这些都表明缺乏特异性结合。未能观察到白蛋白与膜的结合不是由于解离速度过快或“关闭时间”，因为在足够紫外光的存在下孵育以促进配体与受体的共价结合并没有增加结合在膜上的125I计数。最后，在白蛋白/琼脂糖凝胶上亲和层析溶解的膜蛋白，没有提供对白蛋白具有高亲和力的膜蛋白的证据。因此，这些研究不支持肝细胞质膜含有特定白蛋白受体的假设。
To characterize a previously proposed hepatocyte albumin receptor, we examined the binding of native and defatted125I-labeled rat albumin to rat liver plasma membranes. After incubation for 30 min, binding was determined from the distribution of radioactivity between membrane pellet and supernatant following initial centrifugation (15 000 ×gfor 15 min), after repeated cycles of washing with buffer and re-centrifugation.125I-labeled albumin recovered in the initial membrane pellet averaged only 4% of that incubated. Moreover, this albumin was only loosely associated with the membrane, as indicated by recovery in the pellet of under 0.5% of the counts after three washes. Binding of125I-labeled albumin to the plasma membranes was no greater than to erythrocyte ghosts, was not inhibited by excess unlabeled albumin, and was not decreased by heat denaturation of the membranes, all suggestive of a lack of specific binding. Failure to observe albumin binding to the membranes was not due to a rapid dissociation rate or ‘off-time’, as incubations in the presence of sufficient ultraviolet light to promote covalent binding of ligands to receptors did not increase125I counts bound to the membrane. Finally, affinity chromatography over albumin/agarose gel of solubilized membrane proteins provided no evidence of a membrane protein with a high affinity for albumin. These studies, therefore, do not support the hypothesis that liver cell plasma membranes contain a specific albumin receptor.