The protein calbindin-D28k modulates calcium reabsorption in the kidney. Here, we aimed to study the influence of proliferation and apoptosis in different compartments of the kidney on the developmental function of calbindin. Using immunohistochemistry, we investigated the postnatal development of rats' kidneys by using calbindin, proliferative cell nuclear antigen (PCNA), and apoptotic single-stranded DNA (ssDNA). In the neonatal stage (1-day and 1-week-old rats), calbindin showed a positive reaction in the distal convoluted tubule (DCT), a short nephron segment between the macula densa, collecting ducts, and tubules. Moreover, the localization of calbindin was restricted to immature nephrons and mesenchymal tissues. Furthermore, PCNA immunoreactivity was moderate in early-developed podocytes with no reactivity in other renal tubules. The ssDNA immunoreactivity was moderate in the undifferentiated nephron. Then, in the mature stage (3 and 6 weeks old), there was an intense calbindin reaction in DCT but a moderate reaction to PCNA and ssDNA in podocytes. A more intense calbindin reactivity was found in the adult stage (2- and 3-month-old rats) in DCT and collecting tubules. Therefore, in this study, calbindin localization showed an inverse relationship with PCNA and ssDNA of the nephron compartments, which might reflect the efficiency of bone-building and muscle contraction during animal development.

中文翻译：

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钙结合蛋白与出生后大鼠肾脏的增殖和凋亡具有潜在的时空相关性。

蛋白质 calbindin-D28k 调节肾脏中的钙重吸收。在这里，我们的目的是研究肾脏不同区室的增殖和凋亡对钙结合蛋白发育功能的影响。我们利用免疫组织化学方法，利用钙结合蛋白、增殖细胞核抗原 (PCNA) 和凋亡单链 DNA (ssDNA) 来研究大鼠肾脏的出生后发育。在新生儿阶段（1天和1周龄的大鼠），钙结合蛋白在远曲小管（DCT）中显示阳性反应，DCT是致密斑、集合管和肾小管之间的短肾单位段。此外，钙结合蛋白的定位仅限于未成熟的肾单位和间质组织。此外，PCNA 免疫反应性在早期发育的足细胞中中等，而在其他肾小管中没有反应性。未分化肾单位中的 ssDNA 免疫反应性中等。然后，在成熟阶段（3周龄和6周龄），DCT中存在强烈的钙结合蛋白反应，但足细胞中对PCNA和ssDNA的反应中等。在成年阶段（2 个月和 3 个月大的大鼠）DCT 和集合管中发现了更强烈的钙结合蛋白反应性。因此，在本研究中，钙结合蛋白定位显示与肾单位室的 PCNA 和 ssDNA 呈负相关，这可能反映了动物发育过程中骨构建和肌肉收缩的效率。