title: Expression of three isoforms of Na-K-2Cl cotransporter (NKCC2) in the kidney and regulation by dehydration.
abstract: Sodium reabsorption via Na-K-2Cl cotransporter 2 (NKCC2) in the thick ascending limbs has a major role for medullary osmotic gradient and subsequent water reabsorption in the collecting ducts. We investigated intrarenal localization of three isoforms of NKCC2 mRNA expressions and the effects of dehydration on them in rats. To further examine the mechanisms of dehydration, the effects of hyperosmolality on NKCC2 mRNA expression in microdissected renal tubules was studied. RT-PCR and RT-competitive PCR were employed. The expressions of NKCC2a and b mRNA were observed in the cortical thick ascending limbs (CAL) and the distal convoluted tubules (DCT) but not in the medullary thick ascending limbs (MAL), whereas NKCC2f mRNA expression was seen in MAL and CAL. Two-day dehydration did not affect these mRNA expressions. In contrast, hyperosmolality increased NKCC2 mRNA expression in MAL in vitro. Bradykinin dose-dependently decreased NKCC2 mRNA expression in MAL. However, dehydration did not change NKCC2 protein expression in membrane fraction from cortex and outer medulla and in microdissected MAL. These data show that NKCC2a/b and f types are mainly present in CAL and MAL, respectively. Although NKCC2 mRNA expression was stimulated by hyperosmolality in vitro, NKCC2 mRNA and protein expressions were not stimulated by dehydration in vivo. These data suggest the presence of the inhibitory factors for NKCC2 expression in dehydration. Considering the role of NKCC2 for the countercurrent multiplier system, NKCC2f expressed in MAL might be more important than NKCC2a/b.
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Izumi
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Inoue
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Yushi
authors.initials: Y
authors.lastname: Nakayama
authors.affiliation: Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uematsu
authors.affiliation: Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Fukuyama
authors.affiliation: Research Center for Medical Environment, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Taiga
authors.initials: T
authors.lastname: Yamazaki
authors.affiliation: Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Yasuoka
authors.affiliation: Department of Nephrology, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Makino
authors.affiliation: Department of Nephrology, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Nagaba
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Kimio
authors.initials: K
authors.lastname: Tomita
authors.affiliation: Biomedical Laboratory, Division of Biomedical Research, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan.
authors.forename: Noritada
authors.initials: N
authors.lastname: Kobayashi
authors.affiliation: Department of Physiology, Kitasato University School of Medicine, 1-15-1 Kitasato, Sagamihara, Kanagawa 252-0374, Japan.
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Kawahara
authors.affiliation: Department of Nephrology, Kumamoto University Graduate School of Medical Sciences, Faculty of Life Sciences, 1.1.1. Honjo, Chuo-ku, Kumamoto, Kumamoto 860-8556, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Mukoyama
authors.affiliation: Department of Internal Medicine and Education & Research Center, Kitasato University Medical Center, 6-100 Arai, Kitamoto, Saitama 364-8501, Japan. Electronic address: nono@insti.kitasato-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonoguchi
mesh_terms: D000818:Animals; D001483:Base Sequence; D001920:Bradykinin / Q000494:pharmacology; D017931:DNA Primers; D003681:Dehydration / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D007668:Kidney / Q000378:metabolism*; D008297:Male; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D064466:Solute Carrier Family 12, Member 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D020033:Protein Isoforms; D012333:RNA, Messenger; C578716:Slc12a1 protein, rat; D064466:Solute Carrier Family 12, Member 1; D001920:Bradykinin
keywords: Dehydration; Hyperosmolality; Medullary osmotic gradient; Sodium-potassium-2chrolide cotransporter 2 (NKCC2); Vasopressin