Drug Discovery Assay Services Assay: Ion channel function in healthy human tracheal mucosa (Sodium channels)

Code: B063
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Assay type:Respiratory
Tissue:Human Trachea (Mucosa) (Healthy)
Target:Sodium channels
Control Compound:Amiloride
Study Type:Ussing chamber
Functional Endpoint:Ion channel function

Assay Description

This assay asseses whether a test compound causes a change in short circuit current across healthy human tracheal mucosa with amiloride as a reference compound.

The airways of the respiratory tract offer resistance to the flow of air during inhalation and expiration. Any alterations to the airways (for example contractile state, increased mucus or inflammation of the airways) can affect airflow and gas exchange.

Example assay graph

Image Legend

Figure 1: Cumulative concentration response curve to amiloride and its vehicle in isolated human trachea, demonstrating a decrease in Isc following increasing concentrations of amiloride.

The Log EC50 = −6.29 ± 0.21 M (516.4 nM) (mean ± S.E.M), with a maximum response of 114.6 ± 9.45 %.

Testing Information

Introduction

The specific results that will be provided are the effects of increasing concentrations of test articles on the short circuit current across healthy human traceal mucosa.

Turnaround Time

6 weeks from sample receipt for n = 3 donors.

Timelines are a guide based on Biopta's standard tissue criteria; any client imposed deviations to the standard tissue criteria can alter the project timelines.

Test Article Requirements

Test article(s) to be provided by the Sponsor in storable aliquots at required test concentrations with information on diluent vehicle used. Stock solutions are prepared in distilled water unless otherwise requested. Bath volumes are 5 mL; Sponsor to provide sufficient test article to run the entire study.

Suggested Testing

In duplicate at 6 concentrations.

Study Outline

Rationale and Experimental Design

This assay asseses whether a test compound causes a change in short circuit current across healthy human tracheal mucosa with amiloride as a reference compound.

Exclusion Criteria

No specific exclusion criteria are in place other than to reject macroscopically diseased/necrotic tissue. Furthermore, tissues which do not respond to the standard pharmacology checks will be excluded.

Standardisation and Qualification

All lung epithelium tissues are initially processed through standardisation and qualification procedures to ensure functionality, prior to starting the study protocol.

Prior to mounting the epithelium in the Ussing Chambers, the potential difference of the electrodes and the resistance due to the PSS will be offset prior to the experiment. This will ensure that any electrical measurements obtained will be solely tissue derived.

Following mounting of the epithelium the tissue will be allowed to equilibrate before measurements of the tissue potential difference are made.

If the tissue potential difference is satisfactory then the tissue will be placed under voltage clamp and the transepithelial resistance measured.

Tissue will be allowed to equilibrate under voltage clamp conditions before any experimental work is started.

Epithelium samples which pass the qualification pass/fail criteria will then progress to the study protocol.

Ion Channel Assays

To assess their ability to modulate ion channel function, 6 point cumulative concentration response curves (CCRC's) will be performed for each test item. These CCRC's will be performed from stable baseline short circuit current. A positive control compound and representative test article vehicle CCRC will also be run to allow direct comparison with test articles.

An example of the conditions assessed for 3 test articles are detailed below (each condition will be run in duplicate airways):

  • Representative test article vehicle CCRC
  • Positive control CCRC
  • Test article 1 CCRC
  • Test article 2 CCRC
  • Test article 3 CCRC

To assess the involvement of a specific ion channel in any observed responses, a selective ion channel blocker can be added at the end of the test article CCRC.

Analysis

Statistical analysis (where appropriate) will be performed using GraphPad Prism, with the results being shown in graphical form in the final report.

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