title: Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage.
abstract: Potassium Kir4.1/5.1 channels are abundantly expressed at the basolateral membrane of principal cells in the cortical collecting duct (CCD), where they are thought to modulate transport rates by controlling transepithelial voltage. Insulin and insulin-like growth factor-1 (IGF-1) stimulate apically localized epithelial sodium channels (ENaC) to augment sodium reabsorption in the CCD. However, little is known about their actions on potassium channels localized at the basolateral membrane. In this study, we implemented patch-clamp analysis in freshly isolated murine CCD to assess the effect of these hormones on Kir4.1/5.1 at both single channel and cellular levels. We demonstrated that K(+)-selective conductance via Kir4.1/5.1 is the major contributor to the macroscopic current recorded from the basolateral side in principal cells. Acute treatment with 10 μM amiloride (ENaC blocker), 100 nM tertiapin-Q (TPNQ; ROMK inhibitor), and 100 μM ouabain (Na(+)-K(+)-ATPase blocker) failed to produce a measurable effect on the macroscopic current. In contrast, Kir4.1 inhibitor nortriptyline (100 μM), but not fluoxetine (100 μM), virtually abolished whole cell K(+)-selective conductance. Insulin (100 nM) markedly increased the open probability of Kir4.1/5.1 and nortriptyline-sensitive whole cell current, leading to significant hyperpolarization of the basolateral membrane. Inhibition of the phosphatidylinositol 3-kinase cascade with LY294002 (20 μM) abolished action of insulin on Kir4.1/5.1. IGF-1 had similar stimulatory actions on Kir4.1/5.1-mediated conductance only when applied at a higher (500 nM) concentration and was ineffective at 100 nM. We concluded that both insulin and, to a lesser extent, IGF-1 activate Kir4.1/5.1 channel activity and open probability to hyperpolarize the basolateral membrane, thereby facilitating Na(+) reabsorption in the CCD.
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas;
authors.forename: Oleg
authors.initials: O
authors.lastname: Zaika
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and.
authors.forename: Oleg
authors.initials: O
authors.lastname: Palygin
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas; Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russian Federation.
authors.forename: Viktor
authors.initials: V
authors.lastname: Tomilin
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas;
authors.forename: Mykola
authors.initials: M
authors.lastname: Mamenko
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, Wisconsin; and.
authors.forename: Alexander
authors.identifier: http://orcid.org/0000-0002-5190-8356
authors.initials: A
authors.lastname: Staruschenko
authors.affiliation: Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas; Oleh.M.Pochynyuk@uth.tmc.edu.
authors.forename: Oleh
authors.initials: O
authors.lastname: Pochynyuk
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D055724:Electrophysiological Phenomena / Q000187:drug effects; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007685:Kidney Tubules, Collecting / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques; D000081082:Phosphoinositide-3 Kinase Inhibitors; D026902:Potassium Channel Blockers / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000819:agonists / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel
chemical_list: D007004:Hypoglycemic Agents; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D000081082:Phosphoinositide-3 Kinase Inhibitors; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel
keywords: PI3-kinase; distal nephron; nortriptyline; sodium reabsorption; transepithelial transport