title: Increased endothelin-1 expression in the kidney in hypercalcemic rats.
abstract: BACKGROUND
  Although hypercalcemia causes diuresis and natriuresis, the molecular mechanisms of these effects are not well established. Recently, the important role of the calcium-sensing receptor (CaR) in hypercalcemia-induced polyuria was reported. Endothelin-1 (ET-1) that is locally produced in the nephron has been suggested to have the natriuretic and/or diuretic effects in the kidney. Therefore, we hypothesized that ET-1 expression could be increased through the activation of CaR in the kidney in hypercalcemia.
  
  
  METHODS
  Rats were made hypercalcemic by dihydrotachysterol (DHT) treatment. The urinary concentration of ET-1 and the mRNA expression of ET-1 in the kidney were determined. Immunohistochemistry was performed to determine types of the cells that produce ET-1. CaR and ET-1 promoter luciferase constructs were co-expressed in COS-7 cells and the ET-1 promoter activity following the addition of extracellular calcium was measured by the luciferase assay.
  
  
  RESULTS
  In hypercalcemic rat, urinary ET-1 excretion was increased by twofold, and ET-1 mRNA expression was increased in the kidney cortex by threefold. In cortical collecting duct (CCD), both principal cells and intercalated cells synthesized ET-1. In cells that express CaR, ET-1 promoter was activated in a dose-dependent manner by extracellular calcium over the range of 0.5 to 3.0 mmol/L.
  
  
  CONCLUSIONS
  First, activation of CaR increases ET-1 transcription in a dose-dependent manner. Second, hypercalcemia increases ET-1 production in the kidney cortex. These data suggest the possibility that CaR might play an important role in hypercalcemia-induced increase in ET-1 production.
authors.affiliation: Third Department of Internal Medicine, Kumamoto University School of Medicine, Kumamoto, Kumamoto, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Shiraishi
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kitamura
authors.forename: Yukimasa
authors.initials: Y
authors.lastname: Kohda
authors.forename: Takefumi
authors.initials: T
authors.lastname: Narikiyo
authors.forename: Masataka
authors.initials: M
authors.lastname: Adachi
authors.forename: Taku
authors.initials: T
authors.lastname: Miyoshi
authors.forename: Kozo
authors.initials: K
authors.lastname: Iwashita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonoguchi
authors.forename: R Tyler
authors.initials: RT
authors.lastname: Miller
authors.forename: Kimio
authors.initials: K
authors.lastname: Tomita
mesh_terms: D000818:Animals; D019556:COS Cells; D004195:Disease Models, Animal; D004231:Diuresis / Q000502:physiology; D019332:Endothelin-1 / Q000097:blood / Q000235:genetics* / Q000652:urine; D005786:Gene Expression Regulation; D006934:Hypercalcemia / Q000097:blood / Q000503:physiopathology* / Q000652:urine; D007150:Immunohistochemistry; D007672:Kidney Cortex / Q000502:physiology*; D008297:Male; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D044169:Receptors, Calcium-Sensing / Q000378:metabolism
chemical_list: D019332:Endothelin-1; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing