Fatemi S H
Connect Tissue Res. 1987;16(1):1-14. doi: 10.3109/03008208709001990.
Biosynthesis of type IV collagen in the parietal endodermal cells of 12 day gestant Sherman rats was examined following intraconceptal injection of 3H-proline. The concepti were removed at times varying from 2 minutes to 24 hours after the injection. The parietal wall of the yolk sac, including endodermal cells and the associated basement membrane known as Reichert's membrane were processed for electron microscopic radioautography. Silver grains were counted over the organelles of endodermal cells as well as over Reichert's membrane. Radioactivity was high in endodermal cells during the first 2 hr after 3H-proline injection and later dropped to some extent, while radioactivity rose in Reichert's membrane. Examination of endodermal cell organelles showed some early labeling over rER and Golgi apparatus without a clear-cut trend, except for a drop in Golgi label at late times after 3H-proline injection. The density of silver grains over secretory granules rose significantly by 40 min, reached a high peak by 4 hr and then declined at the time when radioactivity increased over Reichert's membrane. Furthermore, the radioactively-labeled secretory granules were localized mainly at the trans Golgi face soon after injection and near the cell surface adjacent to Reichert's membrane at later times. Biochemical reports indicate that a substantial amount of the proline taken up by the 12-14.5 day rat embryo endodermal cells is incorporated into type IV collagen. Since there is high labeling of the secretory granules from 40 min to 4 hr and the labeled granules are associated with the Golgi apparatus at early times, it is proposed that collagen precursors are processed through rER and Golgi apparatus, packaged into secretory granules and then transported to the cell surface where type IV collagen or its precursors are released and subsequently deposited into Reichert's membrane.
在受孕 12 天的 Sherman 大鼠的胚泡内注射 3H-脯氨酸后，检测了壁内胚层细胞中 IV 型胶原的生物合成。在注射后 2 分钟至 24 小时的不同时间取出胚泡。对卵黄囊的壁层，包括内胚层细胞和称为 Reichert 膜的相关基底膜进行电子显微镜放射自显影处理。对内胚层细胞的细胞器以及 Reichert 膜上的银粒进行计数。3H-脯氨酸注射后的最初 2 小时内，内胚层细胞中的放射性很高，随后有所下降，而 Reichert 膜中的放射性则上升。对内胚层细胞器的检查显示，粗面内质网和高尔基体上有一些早期标记，但没有明显的趋势，只是在 3H-脯氨酸注射后的后期高尔基体标记有所下降。分泌颗粒上的银粒密度在 40 分钟时显著上升，在 4 小时时达到高峰，然后在 Reichert 膜上放射性增加时下降。此外，放射性标记的分泌颗粒在注射后不久主要定位于高尔基体反面，后期则靠近与 Reichert 膜相邻的细胞表面。生化报告表明，12 - 14.5 天大鼠胚胎内胚层细胞摄取的大量脯氨酸被掺入 IV 型胶原中。由于在 40 分钟至 4 小时期间分泌颗粒有很高的标记，且标记颗粒在早期与高尔基体相关，因此推测胶原前体通过粗面内质网和高尔基体进行加工，包装成分泌颗粒，然后运输到细胞表面，在那里 IV 型胶原或其前体被释放，随后沉积到 Reichert 膜中。
