Karbach U, Kricke J, Meyer-Wentrup F, Gorboulev V, Volk C, Loffing-Cueni D, Kaissling B, Bachmann S, Koepsell H
Institute of Anatomy of the Bayerische Julius-Maximilians-Universität, 97070 Würzburg, Germany.
Am J Physiol Renal Physiol. 2000 Oct;279(4):F679-87. doi: 10.1152/ajprenal.2000.279.4.F679.
Renal excretion and reabsorption of organic cations are mediated by electrogenic and electroneutral organic cation transporters, which belong to a recently discovered family of polyspecific transporters. These transporters are electrogenic and exhibit differences in substrate specificity. In rat, the renal expression of the polyspecific cation transporters rOCT1 and rOCT2 was investigated. By in situ hybridization, significant amounts of both rOCT1 and rOCT2 mRNA were detected in S1, S2, and S3 segments of proximal tubules. By immunohistochemistry, expression of the rOCT1 protein was mainly observed in S1 and S2 segments of proximal tubules, with lower expression levels in the S3 segments. At variance, rOCT2 protein was mainly expressed in the S2 and S3 segments. Both transporters were localized to the basolateral cell membrane. Neither rOCT1 nor rOCT2 was detected in the vasculature, the glomeruli, and nephron segments other than proximal tubules. The data suggest that rOCT1 and rOCT2 are responsible for basolateral cation uptake in the proximal tubule, which represents the first step in cation secretion.
有机阳离子的肾脏排泄和重吸收由电生性和电中性有机阳离子转运体介导，这些转运体属于最近发现的多特异性转运体家族。这些转运体具有电生性，且在底物特异性上存在差异。在大鼠中，对多特异性阳离子转运体rOCT1和rOCT2的肾脏表达进行了研究。通过原位杂交，在近端小管的S1、S2和S3节段中检测到大量的rOCT1和rOCT2 mRNA。通过免疫组织化学，rOCT1蛋白的表达主要在近端小管的S1和S2节段中观察到，在S3节段中的表达水平较低。与之不同的是，rOCT2蛋白主要在S2和S3节段中表达。两种转运体均定位于基底外侧细胞膜。在脉管系统、肾小球和除近端小管外的肾单位节段中均未检测到rOCT1和rOCT2。数据表明，rOCT1和rOCT2负责近端小管基底外侧阳离子摄取，这是阳离子分泌的第一步。
