Preservation of amino acids is highly important, as these are vital nutrients that support many physiological and biochemical processes. During fish osmoregulation, the kidney reabsorbs amino acids and short peptides that are filtered from the blood into the nephron. However, little is known about reabsorption systems in teleost kidney. To identify transporters involved in this process, we examined by PCR the expression of eight genes, coding to peptide and amino acid transporters, as well as of two ion transport systems, in the kidney of the euryhaline Mozambique tilapia (Oreochromis mossambicus). We found that three amino acid transporters (slc1a5, ASCT2; slc7a9, b^0,+AT; slc6a19, B⁰AT) and one peptide transporter (slc15a2, PepT2) were expressed in the kidney, as were the two ion transporters VHA and NHE3 (coded by atp6v1a and slc9a3, respectively). Next, to investigate transcriptional interactions of these transporters with osmoregulation and nutritional status, we compared by qPCR expression levels in fish acclimated to either fresh or saltwater and at three time points after feeding (6, 24, 72 h). Significant effect of salinity was detected on the expression of ASCT2 and VHA, whereas time after feeding affected PepT2 and VHA transcripts. Interactions between salinity and feeding significantly affected NHE3 transcription. PepT2 expression was an order of magnitude higher than free amino acid transporters, indicating the importance of peptide reabsorption in the kidney of Mozambique tilapia. Immunofluorescence staining of PepT2 showed an apical staining while, b^0,+AT antibody stained the basolateral membrane of the nephrons epithelial cells. The two transporters expression were found in separates segment of the nephrons. These results reveal specific transporters involved in kidney reabsorption of amino acids and short peptides and their response to the fish osmotic and nutritional status.

氨基酸的保存非常重要，因为氨基酸是支持许多生理和生化过程的重要营养素。在鱼渗透调节期间，肾脏会重新吸收从血液中过滤到肾单位的氨基酸和短肽。然而，关于硬骨肾中的重吸收系统知之甚少。为了鉴定参与此过程的转运蛋白，我们通过PCR检测了在莫桑比克罗非鱼（Oreochromis mossambicus）的肾脏中编码肽和氨基酸转运蛋白的八个基因以及两个离子转运系统的表达。我们发现了三个氨基酸转运蛋白（slc1a5，ASCT2; slc7a9，b ^0，+ AT; slc6a19，B ⁰在肾脏中表达了AT）和一个肽转运蛋白（slc15a2，PepT2），以及两个离子转运蛋白VHA和NHE3（由atp6v1a和slc9a3编码）， 分别）。接下来，为了研究这些转运蛋白与渗透压调节和营养状态之间的转录相互作用，我们通过qPCR在摄食后（6、24、72 h）三个时间点适应淡水或咸水的鱼中的表达水平进行了比较。盐度对ASCT2和VHA的表达有显着影响，而进食后的时间影响了PepT2和VHA的转录本。盐度和摄食之间的相互作用显着影响NHE3转录。PepT2表达比游离氨基酸转运蛋白高一个数量级，表明莫桑比克罗非鱼肾脏中肽重吸收的重要性。PepT2的免疫荧光染色显示顶端染色，而b ^0，+AT抗体染色肾单位上皮细胞的基底外侧膜。在肾单位的分开部分中发现了两个转运蛋白表达。这些结果揭示了参与肾脏对氨基酸和短肽的重吸收及其对鱼的渗透和营养状况的反应的特定转运蛋白。