Comparison of Ussing Chambers Systems

Ussing Chamber Systems

December 9, 2024 In Chambers & Sliders

Ussing chambers are an essential tool in physiology research of epithelial transport and barrier function. It is a device used to quantitate the transport of ions and other molecules across epithelial tissues such as the intestine, lung, and kidney.

There are relatively few companies that manufacture Ussing chambers, with the most popular systems being made by Physiologic Instruments and Warner Instruments. This article will compare and contrast Ussing chambers made by these two companies. We concluded based on several key factors that, while both are good systems, the EasyMount system from the Physiologic chamber is the superior product compared to the Navicyte system made by Warner Instruments. Let’s first take a basic look at the two systems starting with the Navicyte system from Warner Instruments.

 

Navicyte Ussing Chamber made by Warner Instruments

Description:  The Ussing chamber made by Warner Instruments is a six-chamber system that is compact, and will fit in most spaces. This system is essentially the “Navicyte” system that was originally developed by Grass and Sweetana in 1988 and later sold to Harvard Bioscience of which Warner Instruments is a subsidiary. The system consists of an anodized aluminum base and back plates, an acrylic front plate and large wingnuts to clamp the chambers between the front and back plates. Water flowing through channels in the front and back plates provides for heating the chambers and air control valves are used to control stirring and oxygenation of the fluids in the chambers.

The system accommodates up to six ussing chambers. Chambers are machined acrylic and are designed with a fixed size aperture to hold a specific tissue. There appears to be about a dozen different chambers available for this system. The Navicyte system features a unique design where steel snap rings on both the front and back securely hold the chamber halves together. Special caps screwed to the chamber top keep the electrodes in place.

These electrodes consist of chlorided silver wire housed in a glass barrel with a porous ceramic frit at the bottom. The barrel is filled with KCl, allowing electrical communication with the solution in the chamber through the ceramic frit. Tissues are generally mounted by stretching over stainless steel pins, although users have made a modification to permit mounting biopsy specimens. Cell cultures grown on Corning snapwell inserts are easily mounted in the chamber designed for cell cultures.

All instruments have their good and bad points. Below we give our opinions of the Warner Navicyte Ussing Chamber:

Pros: 

1. These chambers have been around for more than 30 years.
2. The system is compact.
3. The system looks serviceable and well made.
4. Many research publications have cited this system.

Cons:

There are a number of features we find problematic with the design:

Ussing Chamber heating is not equal between chambers. Researchers heat the chambers using both a metal heat block behind the chamber and a heated acrylic block in front. They secure the chambers between these heat sources by tightening screws at each end of the heating bar. While this seems to be an ideal method, in reality it doesn’t work well because the front heat block bows outwards when tightened at the ends. This results in the chambers at the end having better contact with the heat sources and, thus, higher temperatures than those in the middle.

Ussing Chamber System Electrodes

The electrodes consist of silver wire repeatedly dipped in molten AgCl and inserted into glass capillary tubes. While the electrode wires demonstrate notable stability, the glass barrels are expensive, highly fragile, and prone to breaking during experiments. Additionally, the ceramic frits that separate the KCl inside the glass barrels can vary in thickness. When the frit is too thick, the electrode exhibits very high resistance; when too thin, the saturated KCl inside the barrel can leak into the physiological buffer in the chamber, potentially altering experimental results. Researchers have tested this by placing several KCl-filled barrels in 1 ml of distilled water and measuring the potassium concentration using flame photometry.

Researchers insert all electrodes through the top of the chamber along with the airlines used to stir the solutions. In setups with six chambers positioned side by side, this creates significant congestion, with 24 electrodes and 12 airlines emanating from the chamber tops. Additionally, in many Navicyte chambers, the voltage-sensing electrodes enter at an angle. Removing a single chamber to mount tissue requires removing the electrodes from the chambers on either side. This process is not only inconvenient but also subjects the adjacent electrodes to unnecessary handling, which can alter their offset potential.

Ussing Chamber System Setup

Setup and mounting tissues is a complex procedure. Firstly, researchers must remove the chamber to mount the tissue, which requires removing the electrodes and causes a drop in chamber temperature. Secondly, because the chambers are not independent, mounting tissue in one chamber disrupts the chambers and electrodes on either side. Thirdly, researchers need to disassemble the chambers to mount the tissue and then reassemble them afterward. While this is not a difficult procedure, it does require removing and reinstalling two snap rings and is time consuming.

Researchers must purchase different chambers for different tissues. 

Electrode barrels are easily broken and are expensive; however, as a plus, they can be washed aggressively to remove any drug contaminants. We feel these barrels are too expensive to be considered disposable.

---

EasyMount Ussing Chamber made by Physiologic Instruments

Physiologic Instruments designs the EasyMount Ussing chamber as a modular system that researchers can configure to hold 2, 4, 6, or 8 chambers. They construct the stands from high-quality anodized aluminum and provide separate stations for each chamber. Spring-loaded aluminum cradles hold the acrylic chambers firmly against the heated back plate, ensuring less than a 1-degree temperature variation among chambers. The system uses electrodes made from chlorided silver wire or sintered Ag-AgCl, which fit into modified pipettes that connect through the front of the chamber. The electrode leads run neatly underneath the stand. Valves mounted behind each chamber on the stand regulate airflow. Although this setup is less compact, it offers significant improvements in user-friendliness.

One of the system’s most notable advantages lies in its innovative “slider” technology for mounting tissues. Users can install the tissue slider into the chamber by simply removing the solution, slightly separating the chamber halves, and sliding the tissue into place from the chamber front. This streamlined process takes just 20–30 seconds, compared to over 5 minutes required for the Navicyte chamber. Furthermore, because the electrodes remain undisturbed during the procedure, the system experiences minimal disruption. The design of the EasyMount Ussing chamber system clearly prioritizes reducing the time and effort required for experiments, making it an efficient and user-friendly choice for researchers.

Pros:

1. Temperature uniformity amongst chambers
2. Electrodes are sturdy and researchers can easily prepare the electrode tips themselves or purchase them pre-filled and ready for immediate use.
3. Researchers press the chambers together by turning a thumb screw on the side of the cradle. This mechanism allows them to “feel” the pressure applied, ensuring a proper seal with the tissue and minimizing the risk of “edge-damage.”
4. No need to remove electrodes from the chambers when mounting tissues.
5. Researchers fill the electrode tips with agar or gel, creating a more durable and cost-effective alternative to the fragile glass barrel tips of the Navicyte system.
6. Researchers mount tissues and cell cultures on a slider and then insert them into the chamber, eliminating the need to disassemble the entire chamber, as required with the Navicyte system. This design allows the same chamber to accommodate multiple tissue types, removing the need to purchase a separate chamber for each tissue.
7. Sliders are available for over 20 different tissues and cell culture inserts making this an extremely flexible and more cost effective Ussing system.
8. The top of the EasyMount chamber is much less congested than the Navicyte chamber making it much easier for pipetting operations or for incorporating electrodes such as for pH stat operations.

Superiority of the EasyMount Ussing Chamber by Physiologic Instruments

Warner Instruments offers compact and high-quality Ussing chambers, but we find the EasyMount system from Physiologic Instruments to be superior in nearly every way. The EasyMount Ussing chamber’s design prioritizes experimental accuracy, reproducibility, and ease of use. The design positions its electrode tips precisely within the chamber, ensuring a uniform contact area and minimizing variations in current density. The innovative “slider” technology streamlines tissue mounting and insertion, reducing the risk of contamination or sample damage. This thoughtful design delivers highly accurate and reproducible experimental results.

The slider technology in the EasyMount system offers unmatched versatility. This flexibility allows researchers to use the same chamber for tissues ranging from newborn mouse trachea (P2308, area 0.008 cm²) to adult rabbit intestine (P2315, 1.26 cm²), covering a nearly 160-fold range in tissue aperture area. In comparison, Navicyte’s smallest aperture chamber is the 3 mm round, low-volume chamber (area 0.07 cm²), while the largest is the 8 x 24 mm oblong chamber with pins (area 1.78 cm²), providing only a 25-fold range. Additionally, while a user modification exists for the 8 x 24 mm Navicyte chamber to accommodate endoscopic biopsy specimens (Munch, 2010), Physiologic Instruments directly offers four distinct sliders designed for biopsy specimens.

Customer Support

Physiologic Instruments also excels in customer support. Specializing in equipment for epithelial transport and barrier function research, the company designs and manufactures all its products in Reno, NV. With two Ph.D. scientists on staff who have extensive bench research experience, the company provides exceptional technical support through email, Zoom, phone, and on-site training. Every aspect of the EasyMount system reflects Physiologic Instruments’ in-house expertise.

While Warner Instruments/Harvard Bioscience provides generally favorable product support, it does not match the personalized and in-depth assistance offered by Physiologic Instruments. This disparity likely stems from Warner Instruments’ broad portfolio of instruments and chambers, which limits the depth of expertise in any one area. Additionally, we observed that Warner Instruments did not develop their Ussing chambers in-house; instead, they acquired them from other vendors. This lack of direct design involvement by their own engineers appears to limit the depth and quality of the support they can provide for these systems.

Research Examples

Over the years, scientific researchers have extensively used both the Easymount and Navicyte Ussing systems. Numerous studies have utilized this Ussing chamber to study various aspects of epithelial transport. As examples, in a new article about to be published (Billip et al., 2023), several groups combined data independently garnered using Physiologic Instruments Ussing chamber to evaluate regulation of secretion by chemosensory Tuft cells which is a hallmark of Type 2 immunity. Others have used these systems to study nutrient absorption ( He, et  al., 2013), regulation of gut microbiome (Yin et al, 2017,  Grover & Kashyap, 2014), and effects of cytokines in cystic fibrosis (Rehman et al. 2021 ).

Another study by Wu et al. (2022) utilized the same Ussing chamber to study regulation of ion transport across placental epithelium. Researchers have recently started using Ussing chambers in an exciting new area of study: measuring transport across the blood-brain barrier. Oppong-Damoah et al., 2019 used BEND3 cells grown in culture to form a confluent monolayer and the Ussing chamber to evaluate a nanoparticle drug-delivery system for oxytocin designed to increase its brain bioavailability through active transport.

Summary