title: Intrarenal signaling mediated by CCK plays a role in salt intake-induced natriuresis.
abstract: The natriuretic hormone CCK exhibits its gene transcripts in total kidney extracts. To test the possibility of CCK acting as an intrarenal mediator of sodium excretion, we examined mouse kidneys by1) an in situ hybridization technique for CCK mRNA in animals fed a normal- or a high-sodium diet;2) immuno-electron microscopy for the CCK peptide,3) an in situ hybridization method and immunohistochemistry for the CCK-specific receptor CCKAR;4) confocal image analysis of receptor-mediated Ca2+responses in isolated renal tubules; and5) metabolic cage experiments for the measurement of urinary sodium excretion in high-salt-fed mice either treated or untreated with the CCKAR antagonist lorglumide. Results showed the CCK gene to be expressed intensely in the inner medulla and moderately in the inner stripe of the outer medulla, with the expression in the latter being enhanced by high sodium intake. Immunoreactivity for the CCK peptide was localized to the rough endoplasmic reticulum of the medullary interstitial cells in corresponding renal regions, confirming it to be a secretory protein. Gene transcripts, protein products, and the functional activity for CCKAR were consistently localized to the late proximal tubule segments (S2 and S3) in the medullary rays, and the outer stripe of the outer medulla. Lorglumide significantly diminished natriuretic responses of mice to a dietary sodium load without altering the glomerular filtration rate. These findings suggest that the medullary interstitial cells respond to body fluid expansion by CCK release for feedback regulation of the late proximal tubular reabsorption.
authors.affiliation: Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan hiromiva@med.hokudai.ac.jp.
authors.forename: Hiromi
authors.identifier: 0000-0003-0986-123X
authors.initials: H
authors.lastname: Takahashi-Iwanaga
authors.affiliation: Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kimura
authors.affiliation: Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Kohtarou
authors.initials: K
authors.lastname: Konno
authors.affiliation: Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Department of Anatomy, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iwanaga
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002766:Cholecystokinin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological; D006727:Hormone Antagonists / Q000494:pharmacology; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D007679:Kidney Medulla / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009318:Natriuresis / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043886:Receptor, Cholecystokinin A / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012982:Sodium, Dietary / Q000008:administration & dosage*; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D006727:Hormone Antagonists; D012333:RNA, Messenger; D043886:Receptor, Cholecystokinin A; D012982:Sodium, Dietary; D002766:Cholecystokinin; D002118:Calcium
keywords: Ca2+ image analysis; medullary interstitial cells; proximal tubule; sodium excretion; transmission electron microscopy