Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Pathophysiol. May 15, 2017; 8(2): 59-66
Published online May 15, 2017. doi: 10.4291/wjgp.v8.i2.59
Rectification of oxygen transfer through the rat colonic epithelium
Fernando D Saraví, Graciela E Carra, Daniel A Matus, Jorge E Ibáñez
Fernando D Saraví, Graciela E Carra, Jorge E Ibáñez, Institute of Physiology, Faculty of Medical Sciences, National University of Cuyo, Mendoza 5500, Argentina
Daniel A Matus, Department of Surgery, Faculty of Medical Sciences, National University of Cuyo, Mendoza 5500, Argentina
Jorge E Ibáñez, Mario H. Burgos Institute of Histology and Embryology, CONICET, Faculty of Medical Sciences, National University of Cuyo, Mendoza 5500, Argentina
Author contributions: Saraví FD and Carra GE designed study concept and supervised the experiments; Matus DA and Ibáñez JE performed the experiments and analyzed the data; all authors contributed to data interpretation; Saraví FD drafted the manuscript, which was then critically revised by Carra GE, Matus DA and Ibáñez JE.
Supported by The Secretaría de Ciencia, Técnica y Posgrado, National University of Cuyo, Mendoza 5500 Argentina to Saraví FD, No. 06/J457.
Institutional review board statement: This study was reviewed and approved by the Secretaría de Ciencia y Técnica, National University of Cuyo, institutional review board.
Institutional animal care and use committee statement: All procedures involving the care and use of animals were approved by the Committee for Animal Care and Use of the Faculty of Medical Sciences, National University of Cuyo, Mendoza 5500, Argentina.
Conflict-of-interest statement: There is no conflict of interest.
Data sharing statement: There are no additional data available.
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/
Correspondence to: Fernando D Saraví, MD, PhD, Full Professor, Institute of Physiology, Faculty of Medical Sciences, National University of Cuyo, Parque General San Martín s/n, Mendoza 5500, Argentina. fernando.saravi@hotmail.es
Telephone: +54-261-4135000-2756 Fax: +54-261-4203288
Received: January 26, 2017
Peer-review started: February 8, 2017
First decision: March 9, 2017
Revised: April 12, 2017
Accepted: April 23, 2017
Article in press: April 24, 2017
Published online: May 15, 2017
Abstract
AIM

To assess whether higher sensitivity of colonic epithelium to hypoxia at the serosal side is associated with oxygen transfer asymmetry.

METHODS

Rats were fed either with normal chow or a low-sodium diet. Tissues were mounted as flat sheets in a modified, airtight Ussing chamber with oxygen meters in each hemichamber. Mucosal samples from normal diet animals were studied under control conditions, in low-chloride solution and after adding chloride secretion inhibitors and chloride secretagogues. Samples from sodium-deprived rats were studied before and after ouabain addition. In separate experiments, the correlation between short-circuit current and oxygen consumption was analyzed. Finally, hypoxia was induced in one hemichamber to assess the relationship between its oxygen content and the oxygen pressure difference between both hemichambers.

RESULTS

In all studied conditions, oxygen consumption was larger in the serosal hemichamber than in the mucosal one (P = 0.0025 to P < 0.0001). Short-circuit current showed significant correlation with both total oxygen consumption (r = 0.765; P = 0.009) in normoxia and oxygen consumption in the serosal hemichamber (r = 0.754; P = 0.011) during mucosal hypoxia, but not with oxygen consumption in the mucosal hemichamber. When hypoxia was induced in the mucosal hemichamber, an oxygen pressure difference of 13 kPa with the serosal hemichamber was enough to keep its oxygen content constant. However, when hypoxia was induced in the serosal hemichamber, the oxygen pressure difference with the mucosal hemichamber necessary to keep its oxygen content constant was 40 kPa (P < 0.0001).

CONCLUSION

Serosal oxygen supply is more readily available to support short-circuit current. This may be partly due to a rectifying behavior of transepithelial oxygen transfer.

Keywords: Colonic epithelium, Hypoxia, Oxygen diffusion, Short-circuit current, Ussing chamber

Core tip: The physiological dependence of the colonic epithelium on oxygen provided from the serosal side is not only due to the structure of its blood supply and the low oxygen pressure of colonic intraluminal contents, since it is also observed in isolated mucosa preparations. This study demonstrates for the first time that a much larger partial pressure difference is needed for oxygen transfer from the mucosal side to the serosal side of the epithelium than for transfer in the opposite direction, a phenomenon that may be considered a rectifying behavior.