Christensen E I
Kidney Int. 1976 Oct;10(4):301-10. doi: 10.1038/ki.1976.113.
The aim of the present study was to determine the initial time course for the handling of protein by the proximal tubule cells in rat kidney, using 125I-labeled cytochrome C as a tracer. The uptake of the protein was followed by electron microscope autoradiography in kidneys from rats fixed by perfusion after i.v. injection of cytochrome C. Protein degradation was studied by incubating cortical slices, taken from rats, injected with the same label, and measuring the release of trichloroacetic acid (TCA)-soluble radioactivity from the slices. It was shown by autoradiography that lysosomes in proximal tubule cells start to accumulate labeled cytochrome C within 3 min after injection of the protein, and that the concentration of label in lysosomes increases during the first 30 min after injection, whereas it decreases in endocytic vacuoles. The catabolism of protein as measured in cortical slices began within 13 min after the i.v. injection. Other experiments showed that the accumulation of cytochrome C in the kidneys is very fast. The maximum accumulation, 37% of the injected dose, was reached seven minutes after injection. The results show that protein uptake in proximal tubule cells, transport into lysosomes and the digestion of protein is a more rapid process than previously reported in ultrastructural studies.
本研究的目的是使用125I标记的细胞色素C作为示踪剂，确定大鼠肾脏近端小管细胞处理蛋白质的初始时间进程。静脉注射细胞色素C后，通过灌注固定大鼠的肾脏，利用电子显微镜放射自显影技术追踪蛋白质的摄取。通过孵育取自注射相同标记物的大鼠的皮质切片，并测量切片中三氯乙酸（TCA）可溶性放射性的释放，研究蛋白质降解。放射自显影显示，近端小管细胞中的溶酶体在注射蛋白质后3分钟内开始积累标记的细胞色素C，并且溶酶体中的标记物浓度在注射后的前30分钟内增加，而在内吞泡中则减少。静脉注射后13分钟内，皮质切片中测量的蛋白质分解代谢开始。其他实验表明，细胞色素C在肾脏中的积累非常迅速。注射后7分钟达到最大积累量，为注射剂量的37%。结果表明，近端小管细胞对蛋白质的摄取、向溶酶体的转运以及蛋白质的消化是一个比超微结构研究中先前报道的更快的过程。
