Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage

Oleg Zaika, Oleg Palygin, Viktor Tomilin, Mykola Mamenko, Alexander Staruschenko, Oleh Pochynyuk

Research output: Contribution to journalArticle

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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.

Original languageEnglish (US)
Pages (from-to)F311-F321
JournalAmerican Journal of Physiology - Renal Physiology
Volume310
Issue number4
DOIs
StatePublished - Feb 15 2016

Fingerprint

Somatomedins
Insulin
Nortriptyline
Membranes
Phosphatidylinositol 3-Kinase
Epithelial Sodium Channels
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Amiloride
Fluoxetine
Potassium Channels
Ouabain
Potassium
Sodium
Cell Membrane
Hormones

Keywords

  • Distal nephron
  • Nortriptyline
  • PI3-kinase
  • Sodium reabsorption
  • Transepithelial transport

ASJC Scopus subject areas

  • Physiology
  • Urology

Cite this

Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage. / Zaika, Oleg; Palygin, Oleg; Tomilin, Viktor; Mamenko, Mykola; Staruschenko, Alexander; Pochynyuk, Oleh.

In: American Journal of Physiology - Renal Physiology, Vol. 310, No. 4, 15.02.2016, p. F311-F321.

Research output: Contribution to journalArticle

Zaika, Oleg ; Palygin, Oleg ; Tomilin, Viktor ; Mamenko, Mykola ; Staruschenko, Alexander ; Pochynyuk, Oleh. / Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage. In: American Journal of Physiology - Renal Physiology. 2016 ; Vol. 310, No. 4. pp. F311-F321.
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T1 - Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage

AU - Zaika, Oleg

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AU - Mamenko, Mykola

AU - Staruschenko, Alexander

AU - Pochynyuk, Oleh

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AB - 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.

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KW - PI3-kinase

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KW - Transepithelial transport

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