Ussing chambers are used for investigations into the electrochemical properties of membranes and epithelia, most commonly the mucosae of the gastrointestinal tract or respiratory system.
The setup consists of two fluid-filled, heated, gassed chambers, which are separated only by the mucosal tissue preparation. The illustration below shows a typical set-up for an Ussing chamber system.
Ussing chambers are used for three main purposes:
The measured output from the system relates to the above uses.
For electrophysiology experiments, it is common to record in real-time the potential difference (volts), transepithelial resistance (Ohms.cm2) and short-circuit current (microAmps). Changes in ion channels (e.g. CFTR) or ion exchange mechanisms (e.g. Na-K-Cl cotransporters) result in a change in the short-circuit current. This is of major interest in mucosal tissues because of the role of ion channels in regulating fluid secretion.
With respect to drug absorption, transport and metabolism, Ussing chambers are recognised as the gold standard method by allowing investigations in native 3-D tissues of human or animal origin, ensuring the tissue has a phenotypically-accurate balance of drug-metabolising enzymes and drug transporters. A typical experiment involves the application of a drug to the apical surface of the tissue, followed by periodic sampling of both the apical and basolateral compartments to measure passage of the drug and any metabolites. Oral bioavailability is dependent on a number of factors, two key factors being gastrointestinal permeability and metabolism. A recent review by Astra Zeneca, highlighted the benefits of human fresh tissue mounted in Ussing chambers for the accurate prediction of oral bioavailability. Alternative methods such as Caco-2 cells or intestinal microsomes are useful for either permeability or metabolism experiments, but not both. Moreover, using human fresh gastrointestinal tissue avoids species differences in oral bioavailability.
The third type of experimental readout once again involves the addition of test compounds to the apical and/or basolateral surfaces of the tissue. In this case, however, periodic samples collected from the bathing fluid of the Ussing chambers and/or processing of the tissue at the end of the experiment, offers a flexible method to investigate drug-mediated changes in tissue biology. An increasingly common application is to measure the release of gastrointestinal peptides such as GLP-1 (glucagon-like peptide-1), an incretin released from intestinal epithelial cells in response to nutrients and which stimulates insulin release from the pancreas.
Typical experiments involve 6 to 12 isolated tissue preparations per donor, allowing multiple drugs to be investigated in each experiment. Ussing chambers are a flexible, cost-effective means of investigating mucosal drug transport or drug-mediated effects on tissue behaviour. Contact our scientists today to discuss a protocol that adds commercial value to your compounds through the delivery of human data.
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