Sodium and thallium indicators, which exhibit an increase in fluorescence upon binding Na⁺ or Tl⁺, can be used to measure the activity of sodium channels and transporters.

Sodium Channel Assays

Sodium (Na⁺) in physiology

In most cells at rest, cytoplasmic Na⁺ concentrations are ~5 mM while K⁺ concentrations are above 100 mM. Conversely, extracellular Na⁺ concentrations are typically >100 mM while K⁺ concentrations are in the 3-5 mM range. Therefore, an effective Na⁺ sensor needs to be able to discriminate between K⁺, Na⁺ and other common physiological cations while possessing an appropriate Na⁺ affinity to detect physiologically relevant changes in Na⁺ concentrations.

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Sodium Assays

We’ve used ING-2 AM, our best-in-class sodium indicator, to create the first HTS compatible sodium channel assay that measures intracellular sodium. This kit has been demonstrated to work well for discovering modulators of all voltage-gated sodium channels (Nav1.1-1.9) in addition to ligand-gated channels and Na+-dependent transporters. Interested in exploring more about our sodium indicator collection, click here.

Brilliant Sodium Assays

Brilliant Sodium is the first kit designed to measure intracellular sodium in an HTS-compatible format, so you can discover and characterize the effects of many tens of thousands of compounds and environmental factors on effectors of sodium channels and transporters.

Thallium flux assays for sodium channels

Sodium channel assays using thallium flux

Additional reagents included in all kits for improving indicator loading and retention, and reducing extracellular fluorescence

Although the AM forms of ION’s fluorescent, Na⁺ and Tl⁺ indicators readily cross the plasma membrane, there are other factors that can affect how well the indicators load into cells. Because AM forms of the indicators are quite hydrophobic, it is common to use the non-ionic surfactant, Pluronic F-127, to improve their solubility in aqueous solution thus improving their loading into cells. Pluronic F-127 at the concentrations employed for loading indicators into cells is generally well tolerated. While Pluronic F-127 isn’t absolutely essential for loading most fluorescent Na⁺ and Tl⁺ indicators into cells, it is highly recommended.

Another factor that can affect cell loading and intracellular localization is the presence of anion transport proteins in both plasma and intracellular membranes. In many cell types, the activity of these transporters can result in compartmentalization of the indicators into intracellular compartments as well as extrusion of the indicators outside of the cell. Both of these processes can dramatically reduce the signal-to-background levels and in some cell types (e.g. CHO cells), make adequate loading of Na⁺ and Tl⁺ sensitive fluorescent indicators nearly impossible. Fortunately, probenecid, an organic anion transport inhibitor can be an effective means of inhibiting the transporters, improving cytoplasmic localization and indicator retention. ION offers a convenient, 100X probenecid solution that may be used in conjunction with our Na⁺ and Tl⁺-sensitive fluorescent indicators. While probenecid is generally well-tolerated over the time course of typical experiments using Na⁺ and Tl⁺-sensitive fluorescent indicators, effects on the activity of TRP channels has been reported.

TRS is a masking solution that is composed of a membrane impermeable fluorescence quencher that reduces extracellular fluorescence. Inclusion of this reagent ensures the fluorescence you are measuring is coming from within your cells. Use of this reagent is not recommended for cell suspensions.

Be Brilliant! Explore our line of Sodium Channel Assays and Indicators

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Image Products Excitation Emission Kd Price Quantity Action
Brilliant thallium gold product packaging. A thallium flux assay for potassium channels, sodium channels, and more
Brilliant Thallium Gold
A potassium channel assay, and so much more. Brilliant Thallium Gold includes Thallos Gold - ION’s gold fluorescent (Ex/Em = 528/552 nm) thallium (Tl+) indicator. Red-shifted excitation and emission enable multiplexing with GFP-expressing cells or other green fluorescent indicators. Useful for fluorescence-based potassium (K+) channel assays and for studying a wide variety of monovalent cation channels (sodium channels), transporters, and GPCRs.
$211.00$473.00
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Brilliant thallium gold snapshot assay kit packaging, an option for potassium channel assays, sodium channel assays, and more
Brilliant Thallium Gold Snapshot
Brilliant Thallium Gold Snapshot is a multi-instrument compatible assay solution for well plate-based, high-throughput measurements of thallium flux through potassium, sodium, and non-selective cation channels, as well as some Na+ or K+ transporters. Our patent-pending Snapshot technology generates a long-lasting signal so you can easily detect and quantify changes in ion channel or transporter activity on most fluorescence-capable instruments. The inclusion of Thallos Gold AM, our red-shifted thallium indicator, makes this kit the ideal option when using GFP-expressing cells to run potassium channel assays.
$211.00$473.00
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Brilliant thallium snapshot packaging with an image demonstrating microscope compatibility
Brilliant Thallium Snapshot
An endpoint-compatible potassium channel assay. ION's Brilliant Thallium Snapshot kit is a thallium flux assay adaptation designed to work with standard plate readers, microscopes, flow cytometers, and more, for measuring flux through potassium (K⁺), sodium (Na⁺), and non-selective cation channels, transporters, and their effectors, including GPCRs.
$211.00$473.00
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Thallium flux assay packaging, a potassium channel assay and more
Brilliant Thallium
A potassium channel assay, and so much more. ION’s high-throughput, no wash thallium (Tl⁺) flux assay is an optimal solution for measuring the activity of potassium (K⁺), sodium (Na⁺), and non-selective cation channels and their effectors including transporters and GPCRs.
$211.00$3,597.00
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Brilliant sodium assay kits packaging for sodium channel assays
Brilliant Sodium Assays
Brilliant Sodium is the first high-throughput, no wash sodium channel assay designed to measure changes in intracellular sodium caused by effectors of sodium channels, sodium transporters, and non-selective cation channels.
$228.00$3,623.00
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