Rectification of oxygen transfer through the rat colonic epithelium.

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.

The effects of amiloride and age on oxygen consumption coupled to electrogenic sodium transport in the human sigmoid colon.

Background/aim: Aerobic metabolism is necessary for ion transport in many transporting epithelia, including the human colonic epithelium. We assessed the effects of the epithelial sodium channel blocker, amiloride, on oxygen consumption and short-circuit current of the human sigmoid epithelium to determine whether these effects were influenced by the age of the subject.

Materials And Methods: Segments of the sigmoid colon were obtained from the safety margin of resections performed in patients of 62-77 years of age.

Aldosterone increases oxygen consumption of rectal epithelia of normal, sodium-deprived and sodiumloaded rats.

Introduction: The colonic epithelium is a classical aldosterone target, but the effect of the hormone on the oxygen consumption rate (QO2 ) of this tissue is unknown. Objectives. We aimed at assessing, in the rectal epithelium of rats fed with diets of different sodium content, the effect of epithelial sodium channel (ENaC) blockade on short-circuit current (ISC ) and QO2 , and the acute effect of aldosterone incubation on ISC and QO2 .

The effect of acute hypoxia on short-circuit current and epithelial resistivity in biopsies from human colon.

Background And Aims: In isolated colonic mucosa, decreases in short-circuit current (ISC) and transepithelial resistivity (RTE) occur when hypoxia is either induced at both sides or only at the serosal side of the epithelium. We assessed in human colon biopsies the sensitivity to serosal-only hypoxia and mucosal-only hypoxia and whether Na, K-ATPase blockade with ouabain interacts with hypoxia.

Materials And Methods: Biopsy material from patients undergoing colonoscopy was mounted in an Ussing chamber for small samples (1-mm2 window).

Electrogenic transport, oxygen consumption, and sensitivity to acute hypoxia of human colonic epithelium.

Introduction: It is recognized that epithelial ion transport depends on oxygen supply, but this dependence has not been characterized in the human colon in vitro despite its surgical and clinical implications.

Purposes: The aim of this study is to measure the oxygen consumption of colonic epithelium under conditions which preserve vectorial ion transport and to assess the sensitivity of the human colonic epithelium short-circuit current (I (sc)) to acute hypoxia induced in vitro.

Methods: Isolated mucosa preparations from human sigmoid colon were placed in a modified Ussing chamber which allows simultaneous measurement of short-circuit current (I (sc)) and oxygen consumption (QO(2)).

Effects of chronic hypoxia on electrogenic transport and transport-related oxygen consumption in rat distal colon.

The distal colon epithelium of rats submitted to chronic hypoxia shows higher short-circuit current (Isc) which, unlike non-hypoxic rat epithelium, has an amiloride-sensitive component despite low serum aldosterone levels. Isc and oxygen consumption (QO2) were simultaneously measured in mucosae from rats submitted to 0.5 atm for 10 days and from control rats in a modified Ussing chamber.

Indomethacin reduces short-circuit current and oxygen consumption in normal and chronically hypoxic rat colon.

Chronic hypobaric hypoxia is a physiological environmental stressor. While its effects on most major organ systems have been extensively studied, few works have addressed hypoxia-induced changes in intestinal transport. The effects of cyclooxygenase blockade with indomethacin on short-circuit current (Isc) and oxygen consumption (QO2) of the distal colonic epithelium of control rats and rats submitted to hypoxia for 10 days at 0.

Single-channel response of hamster oocytes to fertilization with homologous spermatozoa.

Electrophysiological events occur early after fertilization, along with changes in intracellular Ca2+ concentration. Passive electrical parameters were determined in golden hamster oocytes by whole cell patch-clamp method. In separate experiments the effect of 4-aminopyridine on resting oocytes was tested.

Increased oxygen consumption caused by cAMP- and Ca(2+)-mediated chloride secretion in rat distal colon.

Epithelial ion transport is dependent on ATP supply provided by aerobic metabolism. In the rat distal colon chloride secretion accounts for the largest portion of electrogenic transport measured as the short-circuit current (I(SC)). Inhibition of basal chloride secretion decreases epithelial oxygen consumption (QO2) in this tissue, while serotonin (5-hydroxytryptamine) proportionally increases both Isc and QO2.

Oxygen consumption and chloride secretion in rat distal colon isolated mucosa.

The aerobic metabolic cost of chloride secretion was studied in rat distal colon isolated mucosa under several conditions by simultaneous measurement of short-circuit current and oxygen consumption under conditions that preserve vectorial ion transport. A low-chloride solution and the presence of bumetanide plus diphenylamine-2-carboxylate reduced short-circuit current by 75% and oxygen consumption by 25%. Ouabain decreased short-circuit current by 93% and oxygen consumption by 32%.