Basic Study
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Exp Med. Dec 19, 2019; 9(2): 14-31
Published online Dec 19, 2019. doi: 10.5493/wjem.v9.i2.14
Localization of ATP-sensitive K+ channel subunits in rat liver
Ming Zhou, Kiwamu Yoshikawa, Hideo Akashi, Mitsutaka Miura, Ryoji Suzuki, Tao-Sheng Li, Hiroshi Abe, Yoshio Bando
Ming Zhou, Hideo Akashi, Ryoji Suzuki, Yoshio Bando, Department of Anatomy, Akita University Graduate School of Medicine, Akita 010-8543, Japan
Kiwamu Yoshikawa, Mitsutaka Miura, Department of Cell Biology and Morphology, Akita University Graduate School of Medicine, Akita 010-8543, Japan
Tao-Sheng Li, Department of Stem Cell Biology, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki 852-8523, Japan
Hiroshi Abe, TRUST, A Long-Term Care Health Facility, Sendai 980-0011, Japan
Author contributions: Zhou M did the main experiments, collected the data, and wrote the paper; Yoshikawa K and Miura M performed the experiment of primary culture for hepatic stellate cells and Kupffer cells; Akashi H and Suzuki R participated in treatment of animals; Li TS, Abe H, and Bando Y supervised the investigation and approved the manuscript for publication.
Supported by the Program of the network-type joint Usage/Research Center for Radiation Disaster Medical Science of Hiroshima University, Nagasaki University, and Fukushima Medical University.
Institutional review board statement: This study was approved by the Animal Research Committee of Akita University.
Institutional animal care and use committee statement: All procedures involving animals were reviewed and approved by the Animal Research Committee of Akita University (a-1-2405).
Conflict-of-interest statement: Authors declare no conflicts of interest for this article.
Data sharing statement: No additional data are available.
ARRIVE guidelines statement: The authors have read the ARRIVE guidelines, and the manuscript was prepared and revised according to the ARRIVE guidelines.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Ming Zhou, MD, PhD, Assistant Professor, Department of Anatomy, Akita University Graduate School of Medicine, 1-1-1 Hondo, Akita 010-8543, Japan. mzhou@med.akita-u.ac.jp
Telephone: +81-18-8846260 Fax: +81-18-8846440
Received: May 17, 2019
Peer-review started: May 20, 2019
First decision: August 2, 2019
Revised: September 5, 2019
Accepted: November 20, 2019
Article in press: November 20, 2019
Published online: December 19, 2019
Abstract
BACKGROUND

ATP-sensitive K+ (KATP) channels were originally found in cardiac myocytes by Noma in 1983. KATP channels were formed by potassium ion-passing pore-forming subunits (Kir6.1, Kir6.2) and regulatory subunits SUR1, SU2A and SUR2B. A number of cells and tissues have been revealed to contain these channels including hepatocytes, but detailed localization of these subunits in different types of liver cells was still uncertain.

AIM

To investigate the expression of KATP channel subunits in rat liver and their localization in different cells of the liver.

METHODS

Rabbit anti-rat SUR1 peptide antibody was raised and purified by antigen immunoaffinity column chromatography. Four of Sprague-Dawley rats were used for liver protein extraction for immunoblot analysis, seven of them were used for immunohistochemistry both for the ABC method and immunofluorescence staining. Four of Wistar rats were used for the isolation of hepatic stellate cells (HSCs) and Kupffer cells for both primary culture and immunocytochemistry.

RESULTS

Immunoblot analysis showed that the five kinds of KATP channel subunits, i.e. Kir6.1, Kir6.2, SUR1, SUR2A, and SUR2B, were detected in liver. Immunohistochemical staining showed that Kir6.1 and Kir6.2 were weakly to moderately expressed in parenchymal cells and sinusoidal lining cells, while SUR1, SUR2A, and SUR2B were mainly localized to sinusoidal lining cells, such as HSCs, Kupffer cells, and sinusoidal endothelial cells. Immunoreactivity for SUR2A and SUR2B was expressed in the hepatocyte membrane. Double immunofluorescence staining further showed that the pore-forming subunits Kir6.1 and/or Kir6.2 colocalized with GFAP in rat liver sections and primary cultured HSCs. These KATP channel subunits also colocalized with CD68 in liver sections and primary cultured Kupffer cells. The SUR subunits colocalized with GFAP in liver sections and colocalized with CD68 both in liver sections and primary cultured Kupffer cells. In addition, five KATP channel subunits colocalized with SE-1 in sinusoidal endothelial cells.

CONCLUSION

Observations from the present study indicated that KATP channel subunits expressed in rat liver and the diversity of KATP channel subunit composition might form different types of KATP channels. This is applicable to hepatocytes, HSCs, various types of Kupffer cells and sinusoidal endothelial cells.

Keywords: ATP-sensitive K+ channel, Liver, Hepatic stellate cells, Kupffer cells, Sinusoidal endothelial cells, Rat

Core tip: ATP-sensitive K+ (KATP) channels have been found to be ubiquitously distributed in a variety of cell types and tissues, but the present study revealed that five kinds of KATP channel subunits are expressed in rat liver by applying western blot analysis, immunohistochemistry, and immunocytochemistry of rat liver tissue and primary cultured cells. These KATP channel subunits were not only localized in hepatocytes but also in sinusoidal cells, such as hepatic stellate cells, Kupffer cells, and sinusoidal endothelial cells. This was demonstrated using specific marker labelling, such as GFAP for hepatic stellate cells, CD68 for Kupffer cells, and SE-1 for sinusoidal endothelial cells. The wide diversity of KATP channel subunit compositions in rat liver might correspond to their various functions in hepatocytes and sinusoidal cells.