Ussing Chamber Methods to Study the Esophageal Epithelial Barrier
The Ussing chamber was developed in 1949 by Hans Ussing and quickly became a powerful tool to study ion and solute transport in epithelia. The chamber has two compartments strictly separating the apical and basolateral sides of the tissue under study. The
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Ussing Chamber Methods to Study the Esophageal Epithelial Barrier Solange M. Abdulnour-Nakhoul and Nazih L. Nakhoul Abstract The Ussing chamber was developed in 1949 by Hans Ussing and quickly became a powerful tool to study ion and solute transport in epithelia. The chamber has two compartments strictly separating the apical and basolateral sides of the tissue under study. The two sides of the tissue are connected via electrodes to a modified electrometer/pulse generator that allows measurement of electrical parameters, namely, transepithelial voltage, current, and resistance. Simultaneously, permeability of the tissue to specific solutes or markers can be monitored by using tracers or isotopes to measure transport from one side of the tissue to the other. In this chapter, we will describe the use of the Ussing chamber to study the barrier properties of the mouse esophageal epithelium. We will also briefly describe the use of the modified Ussing chamber to simultaneously study transepithelial and cellular electrophysiology in the rabbit esophageal epithelium. Lastly, we will cover the use of the Ussing chamber to study bicarbonate secretion in the pig esophagus. These examples highlight the versatility of the Ussing chamber technique in investigating the physiology and pathophysiology of epithelia including human biopsies. Key words Transepithelial, Voltage, Resistance, Short-circuit current, Bicarbonate, pH stat, Stratified squamous, Epithelium, Microelectrodes, Agar bridges, Ion transport, Permeability, Voltage clamp
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Introduction Epithelial cells are held together by intercellular junctions to form sheets of tissue that cover the external surface of the body and line the surface of the gastrointestinal, respiratory, excretory, and reproductive tracts. Epithelial cells are polarized as they have an apical (facing outside or luminal side) and a basolateral membrane (facing blood side). They play important roles in protecting the underlying tissues and in maintaining a stable internal “milieu.” They also have a major role in absorption and secretion. Epithelial transport of ions and solutes could be primary or secondary active [1], or it could be passive through pores and channels [2]. The Ussing chamber has been instrumental to study ion transport in a variety of epithelial tissues including frog skin, toad urinary bladder [3], airways [4], intestine [5], gallbladder [6, 7], stomach [8], and esophagus [9, 10–12].
Solange M. Abdulnour-Nakhoul and Nazih L. Nakhoul
Fig. 1 Hematoxylin & eosin staining of mouse (a) and pig (b) esophageal tissue sections. Submucosal glands (SMG) are present only in pig tissue. SB stratum basalis, SS stratum spinosum, SG stratum granulosum, SC stratum corneum. Bar ¼ 100 μm in a and 1 mm in b
The esophagus is lined with stratified squamous epithelium consisting of multiple cell layers that cover and protect underlying structures from chemical injuries due to ingested food and periodic reflux of acidic stomach contents. According to the KoefoedJohnsen and Ussing, two-membrane model
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