Bissonnette R
Department of Anatomy, McGill University, Montreal, Quebec, Canada.
Cell Tissue Res. 1992 Jan;267(1):131-7. doi: 10.1007/BF00318699.
RNA synthesis was examined by radioautography in mouse duodenal epithelium using 3H-uridine as a tracer of the salvage pathway and 3H-orotic acid as a tracer of the de novo pathway. The incorporation of the two precursors was estimated by counting silver grains in light-microscopic and electron-microscopic radioautographs at successive levels of crypt and villus. With both precursors, silver grains were found over all epithelial nuclei, but in numbers varying by location. Thus, after 3H-uridine injection, the number of grains was high over nucleolus and nucleoplasm in the base of the crypt, declined gradually in the middle and top of the crypt, and was low along the villus. After 3H-orotic acid, the number of grains was fairly low throughout, but peaked over the nucleoplasm in lower villus cells. The 3H-uridine reaction over nucleolus and nucleoplasm in crypt cells was interpreted as synthesis by the salvage pathway of ribosomal RNA and heterogeneous RNA, respectively, whereas the 3H-orotic acid reaction over the nucleoplasm of some villus cells indicated that these cells synthesized heterogeneous RNA by the de novo pathway.
利用³H-尿苷作为补救途径的示踪剂以及³H-乳清酸作为从头合成途径的示踪剂，通过放射自显影术在小鼠十二指肠上皮中检测RNA合成。通过对隐窝和绒毛连续水平的光镜和电镜放射自显影片中的银颗粒进行计数，来估算两种前体的掺入情况。使用这两种前体时，在所有上皮细胞核上均发现有银颗粒，但数量因位置而异。因此，注射³H-尿苷后，隐窝底部核仁和核质上的颗粒数量较多，在隐窝中部和顶部逐渐减少，沿绒毛处则较少。注射³H-乳清酸后，颗粒数量总体上相当少，但在绒毛下部细胞的核质上达到峰值。隐窝细胞内核仁和核质上的³H-尿苷反应分别被解释为核糖体RNA和不均一RNA通过补救途径的合成，而一些绒毛细胞核质上的³H-乳清酸反应表明这些细胞通过从头合成途径合成不均一RNA。
