Introduction to Ussing Systems

Introduction to Ussing Chamber Systems

Researchers generally use an Ussing Chamber System to measure transport across epithelial membranes. This system includes a chamber along with a perfusion system plus an amplifier as well as a data acquisition system if necessary. Within the chamber, several components play supporting roles, while the core functionality of the system resides there. Hans Ussing, a Danish physiologist, first introduced the ‘Classic’ chamber design in the early 1950’s, which remains widely used today. Many importantly improved designs, offering superior convenience along with optimized capabilities for diffusion- or electrophysiology-based measurements, are readily available now.

The apical (or mucosal) and basolateral (or serosal) sides define all epithelia as polar structures. Electrolytes, non-electrolytes, and H₂O play a powerful role in driving this critical movement. Researchers have measured these processes using Ussing systems in various native tissues, such as the stomach, large intestine, small intestine, gall bladder, urinary bladder, skin, and trachea, as well as in cell monolayers derived from renal tubes, pancreas, salivary glands, and sweat glands. A well-designed Ussing chamber isolates each side of an epithelial membrane or cell monolayer, holding it securely in separate chamber halves. This configuration enables complete control, allowing researchers to make highly specific chemical adjustments and precise electrical modifications to each side of the membrane.


Researchers categorized the studies.

Scientists employ Ussing systems for many electrophysiology-based studies, diffusion-based studies, or a combination of both methodologies. Researchers often use these for radiotracer studies where they radiolabel some ionic species undergoing transport. We will, for convenience, treat many radiotracer studies as operating within diffusion-based systems, along with those based on electrophysiology.

A current and/or voltage clamp amplifier, along with a data acquisition system, are incorporated into an electrophysiology-based setup, in addition to the chamber and fluid handling system used by each of the aforementioned approaches. The following components are relevant:

The software, along with the data acquisition system, functioned.

  • A truly thorough systems approach was used.
  • Many diverse Ussing chamber systems, each reflecting importantly different design approaches, exist. Many components’ interchangeability allows for important flexibility, along with wide-ranging customization options.
  • This article outlines the advantages as well as disadvantages of each Ussing chamber design, thus guiding your selection of optimal application components.
Researchers carefully conducted Ussing measurements.

Building an effective Ussing system requires determining the components that best fit your experimental needs, guided by a basic understanding of the commonly performed measurements. Ussing systems are fundamentally classified as either diffusion-based or electrophysiology-based.

Scientists typically use diffusion-based systems to precisely measure transepithelial fluid transport, tracking the net movement of water or solute across the membrane. These systems are particularly suited for studying leaky epithelia with electroneutral transport, though they do not provide detailed information about the underlying transport mechanisms.

Volume changes in the recording chamber, resulting from fluid transport, are usually quantified by measuring changes in a volume marker. Common markers include changes in salt or dye concentration, as well as measurable alterations in physical characteristics like fluid capacitance or resistance. Volume marker-based measurements offer excellent temporal resolution and high sensitivity to small fluxes, with reported detection of volume changes as small as ±1 nl/min. However, the need for extremely small volume chambers is a significant disadvantage.

Electrophysiology-based systems, on the other hand, measure transepithelial electrical responses elicited by experimental perturbations. Researchers use these systems to quantify the activity of electrogenic pathways in the membrane, such as ion pumps and channels. These systems require additional hardware, including a voltage and/or current clamp amplifier, a data acquisition system, and collection/analysis software. Basic measurement parameters include transmembrane voltage (Vt), epithelial membrane resistance (Rt), and short-circuit current (ISC).

While electrophysiology-based systems excel at monitoring electrogenic ion transport, they cannot directly measure non-electrogenic mechanisms like fluid transport or electroneutral ion transport. Researchers address this limitation through indirect or secondary measurements, such as ion replacement techniques, transport inhibition methods, or the application of hormones and second messengers. These approaches provide additional insights into the transport mechanisms that electrophysiology-based systems cannot directly observe.

One measurement technique deserves special attention: the use of radioisotope tracers. Researchers frequently apply this technique to both diffusion-based and electrophysiology-based measurements, effectively elucidating ion-specific transport mechanisms. Diffusion-based models, however, cannot determine whether a fluid’s identity or the cause of a measured volume change—whether hydrostatic or osmotic—is identifiable. Osmotically driven volume changes may involve ionic mechanisms, but these models cannot always identify the key ion involved. Similarly, electrophysiology-based models can measure some ionic transport, but they do not always reveal which specific ion crosses the membrane. This limitation is particularly evident in systems with multiple ionic salts. By using radiolabeled ionic species, researchers can directly monitor ion-specific translocation in both diffusion- and electrophysiology-based systems.

Components of the Ussing chamber system

A single Ussing chamber system consists of a chamber, a perfusion system, and, when necessary, an amplifier and a data acquisition package. To maintain defined temperatures, a circulating water bath thermoregulates the chamber system’s water jackets. The most critical and complex step in assembling a complete Ussing system is choosing the chamber and its tissue support. Addressing this step first simplifies subsequent decisions, making it easier to select the remaining components.

Ussing chambers typically include features for holding the membrane while minimizing tissue damage, exchanging solutions, facilitating precise electrode placement, and controlling solution temperature and gas load.

Several Ussing chamber systems are available, including a Navicyte Horizontal and Vertical ussing chamber systems. A complete ussing chamber system (like Physiologic Instrument’s EasyMount Ussing Chamber System) accommodates various tissue types and cultured cells on permeable supports, such as Snapwell, Millicell, or Transwell inserts. While this system replicates the functionality of Hans Ussing’s classic 1950s design, it differs by using inserts to support tissues and operates with a smaller volume. This system effectively supports cell cultures in Snapwell, Millicell, or Transwell culture cups.

The Navicyte Vertical and Horizontal systems offer highly flexible multiple-channel chamber configurations. These systems include a support assembly that holds one to six independent chambers, facilitates thermal regulation through a water jacket, and integrates perfusion and electronic components with the chambers.

The Navicyte Horizontal system is ideal for studying mucosal layers at an air-liquid interface and can handle between one and six chambers. A mounting ring securely holds the tissue of interest, while Snapwell culture cups can be used to support cultured cells.

For diffusion-based studies, the Navicyte Vertical system excels, accommodating one to six chambers. It eliminates the need for inserts by directly supporting the tissues within the chamber block. A chamber block designed to hold Snapwell culture cups is also available for studying cultured cells.

Electrophysiological measurements

Researchers require an amplifier and a data acquisition system to measure membrane resistance (Rm) or short-circuit current (ISC) across multiple channels. There are several comprehensive data acquisition systems that include amplifiers, digitizers, and software, accommodating configurations of 2, 4, 6, or 8 channels. Detailed information about these systems is available on the UssingChart webpage.