title: Upregulation of calbindin D28k in the late distal tubules in the potassium-loaded adrenalectomized mouse kidney.
abstract: BACKGROUND
  The calcium (Ca)-activated potassium (K) channel is an alternative K-secretory pathway in the apical membranes of the distal nephrons of adrenalectomized (ADX) animals. As a potential approach for estimating intracellular Ca(2+) increase, we investigated normal and ADX mice to determine whether dietary K intake would stimulate the expression of the calbindin D28k protein, a cytosolic Ca(2+)-binding protein, along the distal nephron consisting of the early and late portions of the distal convoluted tubule (DCT1 and DCT2, respectively), the CNT, and CCD.
  
  
  METHODS
  ADX mice received a control diet plus either 0.3% NaCl solution (C) or a 0.3% NaCl plus 3% KCl solution (HK) for 7 days before the experiment.
  
  
  RESULTS
  The mean plasma K concentration and pH were significantly (P < 0.001) higher (7.9 ± 0.3 mEq/l) and lower (7.28 ± 0.02) in the K-loaded ADX mice than in the control ADX mice. The mean urinary K excretion (mEq/day) and urine flow (ml/day) increased significantly (P < 0.0001) from 0.47 ± 0.07 (C) to 4.80 ± 0.57 (HK) and from 1.1 ± 0.2 (C) to 8.8 ± 1.0 (HK). Urinary Ca excretion significantly (P < 0.005 and P < 0.05, respectively) increased in K-loaded normal and ADX mice compared with control normal and ADX mice. Immunofluorescence studies revealed that the relative staining of calbindin was 167.0 ± 15.4%, 291.3 ± 13.8%, and 206.3 ± 11.3% for DCT1, DCT2/CNT, and CCD of normal control mice, respectively. These values increased significantly (P < 0.0001) only in DCT2/CNT (574.8 ± 42%) of the K-loaded ADX mice.
  
  
  CONCLUSIONS
  Upregulation of calbindin in the late distal tubule suggests that Ca(2+)-dependent K transport may function as an alternative mechanism for urinary K excretion in ADX mice.
authors.affiliation: Department of Anesthesiology, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan.
authors.forename: Mizuka
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan.|Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yasuoka
authors.affiliation: Department of Applied Tumor Pathology, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Anatomy, Akita University Graduate School of Medicine and Faculty of Medicine, 1-1-1 Hondo, Akita, Japan.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Department of Anatomy, Akita University Graduate School of Medicine and Faculty of Medicine, 1-1-1 Hondo, Akita, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Abe
authors.affiliation: Department of Cellular and Molecular Physiology, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan. kawahara@kitasato-u.ac.jp.|Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan. kawahara@kitasato-u.ac.jp.
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Kawahara
authors.affiliation: Department of Anesthesiology, Kitasato University Graduate School of Medical Sciences, 1-15-1 Kitasato, Minami-ku, Sagamihara, 252-0374, Japan.
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Okamoto
mesh_terms: D000311:Adrenal Glands / Q000502:physiology*; D000315:Adrenalectomy; D000450:Aldosterone / Q000097:blood; D000818:Animals; D064092:Calbindin 1; D064026:Calbindins; D002118:Calcium / Q000652:urine; D004573:Electrolytes / Q000097:blood / Q000652:urine; D007686:Kidney Tubules, Distal / Q000502:physiology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology; D008297:Male; D051379:Mice; D011188:Potassium / Q000378:metabolism / Q000494:pharmacology* / Q000652:urine; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis*; D015854:Up-Regulation; D014667:Vasopressins / Q000652:urine
chemical_list: C576499:Calb1 protein, mouse; D064092:Calbindin 1; D064026:Calbindins; D004573:Electrolytes; D051036:Large-Conductance Calcium-Activated Potassium Channels; D064030:S100 Calcium Binding Protein G; D014667:Vasopressins; D000450:Aldosterone; D011188:Potassium; D002118:Calcium