Christensen N J, Rubin C E, Cheung M C, Albers J J
J Lipid Res. 1983 Sep;24(9):1229-42.
Apolipoprotein B (apoB) was localized by electron microscopy within absorptive cells of human jejunal biopsy specimens taken fasting and after micellar fat infusion. Nakane's double antibody immunoperoxidase technique was used to label apoB near open cut surfaces of 60-Micrometers fixed tissue slices sectioned by a Ralph knife in a Vibratome. In fasting tissue, apoB label was found within structurally intact peri-mitochondrial rough endoplasmic reticulum (RER) and within Golgi cisternae of absorptive cells covering the tips of jejunal villi. After fat infusion, apoB label was found adjacent to very low density lipoproteins (VLDL) and chylomicrons within apical smooth endoplasmic reticulum (SER). Less label was seen within RER than in fasting absorptive cells, and RER-SER connections containing apoB label were occasionally seen. Expanded Golgi vesicles and cisternae contained VLDL, chylomicrons, and apoB label. Vesicles containing chylomicrons and apoB label were occasionally visualized bordering the lateral plasma membrane in a configuration suggesting exocytosis. Specific apoB label was regularly seen within intercellular spaces and capillaries, but the in vivo significance of this Localization was problematical. These observations suggest that apoB is synthesized in RER, transfers to SER where it is incorporated into new VLDL and chylomicrons, and moves to Golgi cisternae and vesicles to be prepared for exocytosis through the plasma membrane.
采用电子显微镜技术，对空腹及给予微粒脂肪灌注后的人空肠活检标本中的吸收细胞进行载脂蛋白B（apoB）定位研究。应用中根氏双抗体免疫过氧化物酶技术，对用振动切片机上的拉尔夫刀切割成60微米厚的固定组织切片开放表面附近的apoB进行标记。在空腹组织中，apoB标记物见于空肠绒毛顶端覆盖的吸收细胞结构完整的线粒体周围粗面内质网（RER）内以及高尔基池内。脂肪灌注后，apoB标记物见于顶端滑面内质网（SER）内与极低密度脂蛋白（VLDL）和乳糜微粒相邻处。与空腹吸收细胞相比，RER内的标记物较少，偶尔可见含apoB标记物的RER-SER连接。扩张的高尔基小泡和池内含有VLDL、乳糜微粒和apoB标记物。偶尔可见含乳糜微粒和apoB标记物的小泡以一种提示胞吐作用的形态靠近侧质膜。在细胞间隙和毛细血管内经常可见特异性apoB标记物，但这种定位在体内的意义尚存在问题。这些观察结果提示，apoB在RER中合成，转移至SER并在其中被整合到新的VLDL和乳糜微粒中，并转移至高尔基池和小泡，为通过质膜进行胞吐作用做好准备。
