Sabolić Ivan, Skarica Mario, Gorboulev Valentin, Ljubojević Marija, Balen Daniela, Herak-Kramberger Carol M, Koepsell Hermann
Unit of Molecular Toxicology, Institute for Medical Research and Occupational Health, Ksaverska cesta 2, 10001 Zagreb, Croatia.
Am J Physiol Renal Physiol. 2006 Apr;290(4):F913-26. doi: 10.1152/ajprenal.00270.2005. Epub 2005 Oct 4.
SGLT1 (SLC5A1) mediates a part of glucose and galactose reabsorption in the mammalian proximal tubule (PT), but the detailed localization of the transporter along the tubule is still disputable. Here, we used several methods to localize rat SGLT1 (rSGLT1) in the kidneys of intact and variously treated male (M) and female (F) rats. In immunoblots of isolated cortical (C) and outer stripe (OS) brush-border membranes (BBM), a peptide-specific polyclonal antibody for rSGLT1 labeled a sharp inzone-, and gender-dependent approximately 40-kDa protein and a broad approximately 75-kDa band that exhibited strong zonal (OS > C) and gender differences (F > M). In tissue cryosections, the antibody strongly stained BBM of the S3 PT segments in the OS and medullary rays (F > M) and smooth muscles of the blood vessels and renal capsule (F approximately M) and weakly stained the apical domain of other PT segments in the C (F approximately M). The phlorizin-sensitive uptake of d-[(3)H]galactose in BBM vesicles, as well as the tissue abundance of rSGLT1-specific mRNA, matched the immunoblotting data related to the 75-kDa protein and the immunostaining in S3, proving zonal and gender differences in the functional transporter. Ovariectomy had no effect, castration upregulated, whereas treatment of castrated rats with testosterone, but not with estradiol or progesterone, downregulated the 75-kDa protein and the immunostaining in S3. We conclude that in the rat kidney, the expression of SGLT1 is represented by a 75-kDa protein localized largely in the PT S3 segments, where it exhibits gender differences (F > M) at both the protein and mRNA levels that are caused by androgen inhibition.
钠-葡萄糖协同转运蛋白1（SGLT1，溶质载体家族5成员1）介导哺乳动物近端小管（PT）对部分葡萄糖和半乳糖的重吸收，但该转运体沿肾小管的详细定位仍存在争议。在此，我们采用多种方法在完整及经过不同处理的雄性（M）和雌性（F）大鼠肾脏中定位大鼠SGLT1（rSGLT1）。在分离的皮质（C）和外带（OS）刷状缘膜（BBM）的免疫印迹中，一种针对rSGLT1的肽特异性多克隆抗体标记出一条尖锐的、与区域和性别相关的约40 kDa蛋白条带以及一条较宽的约75 kDa条带，后者表现出强烈的区域差异（OS＞C）和性别差异（F＞M）。在组织冰冻切片中，该抗体强烈染色OS和髓放线中S3近端小管节段的BBM（F＞M）以及血管和肾被膜的平滑肌（F≈M），并微弱染色C中其他近端小管节段的顶端区域（F≈M）。BBM囊泡中根皮苷敏感的d-[(3)H]半乳糖摄取以及rSGLT1特异性mRNA的组织丰度与75 kDa蛋白的免疫印迹数据及S3中的免疫染色相匹配，证实了功能性转运体存在区域和性别差异。卵巢切除术无影响，去势上调，而用睾酮而非雌二醇或孕酮处理去势大鼠则下调75 kDa蛋白及S3中的免疫染色。我们得出结论，在大鼠肾脏中，SGLT1的表达由一种主要定位于近端小管S3节段的75 kDa蛋白代表，该蛋白在蛋白质和mRNA水平均表现出性别差异（F＞M），这是由雄激素抑制所致。
