title: Role of pituitary in K+ homeostasis: impaired renal responses to altered K+ intake in hypophysectomized rats.
abstract: The kidneys maintain extracellular K⁺ homeostasis by altering K⁺ excretion to match K⁺ intake. Because this can occur without changes in plasma K⁺ concentrations ([K⁺]), how the kidneys sense K⁺ intake is unclear. We tested the hypothesis that the pituitary plays a critical role in signaling K⁺ intake to the kidneys. If this hypothesis is true, hypophysectomy would impair kidney responses to altered K⁺ intake. Hypophysectomized (Hypox) and sham-operated control rats (n = 8 each) were compared for their abilities to adjust K⁺ excretion during a transition from normal to reduced (to one-third of normal) K⁺ intake, followed by a reversal to normal K⁺ intake. Food was provided only at night, and renal K⁺ excretion was determined both for absorptive (night or feeding) and postabsorptive (day or nonfeeding) periods. In normal rats, both absorptive and postabsorptive renal K⁺ excretion were changed in parallel to the changes in K⁺ intake, indicating a rapid adaptation of normal kidneys to altered K⁺ intake. In Hypox rats, whereas absorptive renal K⁺ excretion was changed in response to changes in K⁺ intake, postabsorptive K⁺ excretion was not responsive (P < 0.001), indicating impaired renal responses to altered K⁺ intake. In addition, Hypox rats, compared with control rats, showed K⁺ intolerance (increases in plasma [K⁺]) upon feeding (i.e., K⁺ intake) at night or following an intravenous K⁺ infusion (P < 0.01), indicating an impairment of acute renal responses to K⁺ intake. These data support that the pituitary plays a key role in the signaling of K⁺ intake to the kidneys (and kidney responses to altered K⁺ intake).
authors.affiliation: Department of Physiology and Biophysics, University of Southern California, Keck School of Medicine, Los Angeles, CA 90089, USA.
authors.forename: Young Taek
authors.initials: YT
authors.lastname: Oh
authors.forename: Jinyub
authors.initials: J
authors.lastname: Kim
authors.forename: Jang H
authors.initials: JH
authors.lastname: Youn
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000450:Aldosterone / Q000097:blood; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology; D003345:Corticosterone / Q000494:pharmacology; D006706:Homeostasis / Q000502:physiology*; D007016:Hypophysectomy; D007262:Infusions, Intravenous; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D023421:Models, Animal; D010902:Pituitary Gland / Q000502:physiology* / Q000601:surgery; D011188:Potassium / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D017419:Potassium, Dietary / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology
chemical_list: D017419:Potassium, Dietary; D000450:Aldosterone; D011188:Potassium; D003345:Corticosterone
keywords: brain; gut factor; potassium excretion; potassium sensing; potassium tolerance