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KMID : 0363720070400010011
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Korean Journal of Anatomy
2007 Volume.40 No. 1 p.11 ~ p.25
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Immunocytochemical Study of Calbindin D28k Positive Cells in the Developing Rat Kidney
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Park Eun-Young
Lee Hyun-Wook
Song Hyun-Kuk
Hwang Jin-Sun
Kim Wan-Young
Kim Jin
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Abstract
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Calbindin D28k, a calcium binding protein, is found in various tissues, including some cells in the distal nephron. It plays an important role in the regulation of calcium reabsorption. We previously reported the expression of calbindin D28k in adult rat kidney. However, the exact time of expression during differentiation in the embryonic kidney is not known.During development, intercalated cells are deleted from the medullary collecting duct by two distinct mechanisms. However, the reason for the different modes of cell death is not known. As calbindin is reported to protect cells against apoptosis, we examined the expression of calbindin D28k in the developing rat kidney. Kidneys from 16-, 17-, 18- and 20-day-old fetuses and 1-, 3-, 5-, 7-, 14- and 21-day-old pups and adult Sprague Dawley rats were processed for immunohistochemistry using a monoclonal antibody against calbindin D28k. Intercalated cells were identified by immunostaining for H+-ATPase and by electron microscopy. Calbindin D28k immunoreactivity first appeared in subpopulations of cells in the connecting tubule and medullary collecting duct in the 17-day-old fetus. In the connecting tubule, calbindin D28k was expressed only in H+-ATPase negative connecting tubule cells, and there was no labeling of intercalated cells. In the medullary collecting duct, calbindin D28k immunostaining was observed in a few cells with apical H+-ATPase, characteristic of type A intercalated cells. The numbers of calbindin D28k-positive type A intercalated cells increased from day 18 of gestation. In contrast, there was little or no calbindin D28k immunoreactivity in the type B intercalated cells or principal cells. During the first two weeks after birth, calbindin D28k-positive type A intercalated cells were lost from the terminal part of the medullary collecting duct by simple extrusion. After two weeks, calbindin D28k immunostaining decreased in the type A intercalated cells throughout the medullary collecting duct. However, the immunoreactivity of calbindin D28k in the cortical collecting duct was increased in some of the type A intercalated cells and the adult pattern was observed in 21-day-old pups. Thus, we propose that the different expression of calbindin D28k in type A and type B intercalated cells may be responsible-at least partly-for the different modes of cell death demonstrated in these cells during kidney development.
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KEYWORD
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Calbindin D28k, Intercalated cell, Developing rat kidney, Immunohistochemistry
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