山梨医科大学雑誌　第15巻2号　027-038(2000)

Immunohistochemical Localization of Calcium-Sensing
Receptor in the Rat Kidney

Sawako KOISHI, Kaoru AIDA, Masato TAWATA, Shinichi OHNO and Toshimasa ONAYA

Abstract: Calcium-sensing receptor (CaSR) plays a pivotal role in calcium homeostasis. Although CaSR mRNA has been detected in the kidney, its precise location is not known. We generated a polyclonal antibody against the extracellular domain of human kidney CaSR and studied its localization by immunohistochemical methods. By Western blotting, our anti-CaSR antibody recognized bands with molecular weights of 120 and 75kDa from rat medullary thyroid carcinoma cell line, rMTC 6-23. However, when crude membrane fractions were prepared from rMTC 6-23 and rat kidneys, only an 80 kDa band was detected, probably due to degradation. Immunohistochemical study with a light microscope showed that CaSR localized in the thick ascending limb of HenleOs loop and distal convoluted tubules, and was not found in any other nephron segments. The immunostaining in the epithelial cells was observed at their basal parts, presumably along the basal infolding. Almost all of the epithelial cells in the thick ascending limb were stained but the cells of distal convoluted tubules were heterogeneously stained. In an electron microscope study, staining was found along the cell membrane of the basal infolding. These results indicate that in the rat kidney, CaSR locates in the basal membranes of the thick ascending limb and distal convoluted tubules and suggest that CaSR senses extracellular (peritubular, not luminal) Ca2＋ concentrations and plays an important role in calcium reabsorption.

Key words: Calcium-sensing receptor, kidney, thick ascending limb of the Henle's loop, distal convoluted tubules, calcium absorption.




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