Hellfritzsch M, Christensen E I, Sonne O
Kidney Int. 1986 May;29(5):983-8. doi: 10.1038/ki.1986.97.
It is generally accepted that proteins taken up from the renal tubular fluid are transported into lysosomes in proximal tubule cells. Recently, however, it has been postulated that insulin in isolated perfused rat kidneys did not accumulate in lysosomes but to a certain degree in the Golgi region. The present study was undertaken to investigate the intracellular handling of biologically unaltered insulin in rat renal proximal tubule cells. Rats were prepared for in vivo micropuncture and either a colloidal gold insulin complex or insulin monoiodinated in the A-14 position (125I-insulin) was microinfused into proximal tubules. After 5, 10, 25 or 60 min the tubules were fixed by microinfusion of glutaraldehyde and processed for electron microscopy or electron microscope autoradiography. A qualitative analysis of tubules infused with colloidal gold insulin or 125I-insulin showed that insulin was taken up by endocytosis and transported to lysosomes, and a quantitative autoradiographic analysis of the 125I-insulin microinfused tubules showed that the grain density after five min was significantly increased for endocytic vacuoles and for lysosomes. After 60 min the grain density was still significant over lysosomes. The accumulation of grains was non-significant over all other areas analyzed at any time. This study shows that insulin is taken up from the luminal side of the proximal tubule by endocytosis and transported to the lysosomes. There was no significant transport to the Golgi region.
一般认为，从肾小管液中摄取的蛋白质会被转运到近端小管细胞的溶酶体中。然而，最近有人推测，在离体灌注的大鼠肾脏中，胰岛素并非积聚在溶酶体中，而是在一定程度上积聚在高尔基体区域。本研究旨在探讨大鼠肾近端小管细胞中未发生生物学改变的胰岛素在细胞内的处理情况。对大鼠进行体内微穿刺准备，将胶体金胰岛素复合物或A-14位单碘化胰岛素（125I-胰岛素）微注入近端小管。5、10、25或60分钟后，通过微注入戊二醛固定小管，并进行电子显微镜或电子显微镜放射自显影处理。对注入胶体金胰岛素或125I-胰岛素的小管进行定性分析表明，胰岛素通过内吞作用被摄取并转运至溶酶体，对微注入125I-胰岛素的小管进行定量放射自显影分析表明，5分钟后，内吞小泡和溶酶体的颗粒密度显著增加。60分钟后，溶酶体上的颗粒密度仍然显著。在任何时候，在所有其他分析区域，颗粒的积聚均不显著。本研究表明，胰岛素通过内吞作用从近端小管的管腔侧被摄取并转运至溶酶体。向高尔基体区域的转运不显著。
