Glaumann H, Ericsson J L
J Cell Biol. 1970 Dec;47(3):555-67. doi: 10.1083/jcb.47.3.555.
A comparative biochemical and radioautographic in vivo study was performed to identify the site of synthesis and route of migration of albumin in the parenchymal liver cell after labeling with leucine-(14)C or leucine-(3)H via the portal vein. Free cytoplasmic ribosomes, membrane-bound ribosomes, rough- and smooth-surfaced microsomes, and Golgi membranes were isolated. The purity of the Golgi fraction was examined morphologically and biochemically. After administration of leucine-(14)C, labeled albumin was extracted, and the sequence of transport was followed from one fraction to the other. Approximately 2 min after the intravenous injection, bound ribosomes displayed a maximal rate of leucine-(14)C incorporation into albumin. 4 min later, a peak was reached for rough microsomes. Corresponding maximal activities for smooth microsomes were recorded at 15 min, and for the Golgi apparatus at approximately 20 min. The relative amount of albumin, calculated on a membrane protein basis, was higher in the Golgi fraction than in the microsomes. By radioautography the silver grains were preferentially localized over the rough-surfaced endoplasmic reticulum at the 5 min interval. Apparent activity in the Golgi zone was noted 9 min after the injection; at 15 and 20 min, the majority of the grains were found in this location. Many of the grains associated with the Golgi apparatus were located over Golgi vacuoles containing 300-800 A electron-opaque bodies. It is concluded that albumin is synthesized on bound ribosomes, subsequently is transferred to the cavities of rough-surfaced endoplasmic reticulum, and then undergoes migration to the smooth-surfaced endoplasmic reticulum and the Golgi apparatus. In the latter organelle, albumin can be expected to be segregated together with very low density lipoprotein in vacuoles known to move toward the sinusoidal portion of the cell and release their content to the blood.
进行了一项比较性的生物化学和放射自显影体内研究，以确定经门静脉用亮氨酸 -（14）C 或亮氨酸 -（3）H 标记后，实质肝细胞中白蛋白的合成部位和迁移途径。分离出游离细胞质核糖体、膜结合核糖体、粗面和滑面微粒体以及高尔基体膜。从形态学和生物化学方面检查了高尔基体部分的纯度。给予亮氨酸 -（14）C 后，提取标记的白蛋白，并追踪其从一个部分到另一个部分的运输顺序。静脉注射后约 2 分钟，结合核糖体将亮氨酸 -（14）C 掺入白蛋白的速率达到最大值。4 分钟后，粗面微粒体达到峰值。滑面微粒体在 15 分钟时记录到相应的最大活性，高尔基体在约 20 分钟时达到最大活性。以膜蛋白为基础计算，高尔基体部分中白蛋白的相对含量高于微粒体。通过放射自显影，在 5 分钟间隔时，银颗粒优先定位在粗面内质网上。注射后 9 分钟在高尔基体区域观察到明显活性；在 15 分钟和 20 分钟时，大部分颗粒位于该位置。与高尔基体相关的许多颗粒位于含有 300 - 800 Å 电子不透明体的高尔基体液泡上。得出的结论是，白蛋白在结合核糖体上合成，随后转移到粗面内质网腔中，然后迁移到滑面内质网和高尔基体。在后者的细胞器中，预计白蛋白会与极低密度脂蛋白一起在已知向细胞窦状部分移动并将其内容物释放到血液中的液泡中分离。
