Berka J L, Alcorn D, Ryan G B, Skinner S L, Weaver D A
Department of Anatomy, University of Melbourne, Parkville, Victoria, Australia.
J Histochem Cytochem. 1993 Mar;41(3):365-73. doi: 10.1177/41.3.8429199.
We examined renin processing in cultured juxtaglomerular (JG) cells of the hydronephrotic mouse kidney with immunocytochemical and biochemical techniques. Compared with JG cells in normal kidneys, there was less intense labeling for renin protein in mature granules of cultured JG cells. However, pro-renin labeling of transport vesicles and juvenile granules was maintained, suggesting incomplete passage of pro-renin through intermediate and mature granules. Immunogold evidence of exocytosis of mature granules containing renin protein was present at all stages. Labeling of transport vesicles for pro-renin, together with the absence of exocytosis of pro-renin from juvenile granules, indicated that pro-renin was exclusively released by a constitutive process. Active renin release into supernatants decreased with time, whereas the ratio of total renin to active renin increased, indicating that pro-renin synthesis and release were maintained but that the processing of pro-renin to active renin was interrupted. Angiotensin II inhibited and verapamil stimulated active renin release in culture; neither substance affected pro-renin release. Application of secretagogues that act via intracellular calcium or cAMP resulted in depletion of mature granules and their deformation by myelin figures and vacuoles, findings consistent with an exocytosis from mature granules. The absence of effect of any secretagogues on pro-renin release suggests that these stimulatory mechanisms are exclusively post-Golgi. In cultured JG cells in renal explants, renin vesicular transport and granular exocytosis are maintained but a defect in pro-renin passage from juvenile to intermediate granules is apparent.
我们运用免疫细胞化学和生化技术，研究了肾积水小鼠肾脏培养的球旁（JG）细胞中的肾素加工过程。与正常肾脏中的JG细胞相比，培养的JG细胞成熟颗粒中肾素蛋白的标记强度较低。然而，前肾素在转运囊泡和幼稚颗粒中的标记得以维持，这表明前肾素在中间颗粒和成熟颗粒中的加工过程不完全。在所有阶段均存在含肾素蛋白的成熟颗粒胞吐作用的免疫金证据。前肾素在转运囊泡上的标记，以及幼稚颗粒中前肾素不存在胞吐作用，表明前肾素仅通过组成型过程释放。活性肾素释放到上清液中的量随时间减少，而总肾素与活性肾素的比例增加，这表明前肾素的合成和释放得以维持，但前肾素加工为活性肾素的过程被中断。血管紧张素II抑制培养物中活性肾素的释放，维拉帕米则刺激其释放；这两种物质均不影响前肾素的释放。应用通过细胞内钙或环磷酸腺苷起作用的促分泌剂，导致成熟颗粒耗竭及其被髓鞘样结构和空泡变形，这些发现与成熟颗粒的胞吐作用一致。任何促分泌剂对前肾素释放均无影响，这表明这些刺激机制仅在高尔基体后起作用。在肾外植体培养的JG细胞中，肾素囊泡运输和颗粒胞吐作用得以维持，但前肾素从幼稚颗粒到中间颗粒的加工缺陷明显。
