Participation of molecular determinants of endocytosis in the processes of glomerular filtration and tubular reabsorption of albumin and lysozyme in the mesonephros of grass frogs (Rana temporaria L.), lake frogs (Rana ridibunda P.), and newts (Triturus vulgaris L.) is investigated. In all studied species, the constitutive expression of endocytic receptors in proximal tubule (PT) cells is established using immunofluorescence microscopy and immunoblotting. The certain stages of lysozyme and albumin endocytosis involving megalin/LRP2, cubilin, clathrin and protein Rab11 are detailed, and the central role of ligand-induced megalin/LRP2 activity in this process is shown. Increased ligand-induced expression for clathrin and Rab11was also found. In grass frogs, the different patterns of endocytic receptors and both absorbed proteins in the initial parts of proximal tubules suggest the proximo-distal specialization of absorptive processes along these tubule segments, similar to this in more complex mammalian nephrons. This data, as well as the revealed peculiarities of ligand-receptor interactions during intracellular trafficking of proteins prove that megalin is mainly involved in the absorption of lysozyme. At the same time, albumin absorption is mediated by both receptors, or cubilin contributes the most. The detection of endocytic receptor in glomerular structural elements in frogs and newts suggests the participation of filtration barrier components in endocytosis of filterable proteins. The results represent a new contribution to the study of the fundamental mechanisms of renal protein uptake in the amphibian mesonephros as a more primitive kidney compared to mammalian metanephros.

草蛙 ( Rana temporaria L.)、湖蛙 ( Rana ridibunda P.) 和蝾螈 ( Triturus vulgarisL.) 进行调查。在所有研究的物种中，近端小管 (PT) 细胞中内吞受体的组成型表达是使用免疫荧光显微镜和免疫印迹法确定的。详细介绍了涉及巨蛋白/LRP2、cubilin、网格蛋白和蛋白质 Rab11 的溶菌酶和白蛋白内吞作用的某些阶段，并显示了配体诱导的巨蛋白/LRP2 活性在此过程中的核心作用。还发现网格蛋白和 Rab11 的配体诱导表达增加。在草蛙中，近端小管初始部分的内吞受体和两种吸收蛋白质的不同模式表明，沿着这些小管节段的吸收过程的近远端特化，类似于更复杂的哺乳动物肾单位。这个数据，以及在细胞内运输蛋白质过程中所揭示的配体-受体相互作用的特性证明，巨蛋白主要参与溶菌酶的吸收。同时，白蛋白吸收由两种受体介导，或cubilin贡献最大。在青蛙和蝾螈的肾小球结构元件中检测到内吞受体表明过滤屏障成分参与了可过滤蛋白质的内吞作用。与哺乳动物后肾相比，该结果代表了对研究两栖动物中肾作为更原始肾脏的肾蛋白摄取的基本机制的新贡献。或cubilin贡献最大。在青蛙和蝾螈的肾小球结构元件中检测到内吞受体表明过滤屏障成分参与了可过滤蛋白质的内吞作用。与哺乳动物后肾相比，该结果代表了对研究两栖动物中肾作为更原始肾脏的肾蛋白摄取的基本机制的新贡献。或cubilin贡献最大。在青蛙和蝾螈的肾小球结构元件中检测到内吞受体表明过滤屏障成分参与了可过滤蛋白质的内吞作用。与哺乳动物后肾相比，该结果代表了对研究两栖动物中肾作为更原始肾脏的肾蛋白摄取的基本机制的新贡献。