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

Thallium flux assay example, showing fluorescence images of Thallos loaded cells before and after the addition of Thallium (Tl+)

Thallium flux assay packaging, a potassium channel assay and more

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Brilliant Thallium

$211.00

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Brilliant Thallium Gold Snapshot

$211.00

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Brilliant Thallium Gold

$211.00

Dose response curves of a voltage-gated sodium channel assay, Nav1.3, treated using tetracaine, using both kinetic and endpoint assay formats.

Brilliant sodium assay kits packaging for sodium channel assays

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Brilliant Sodium Assays

$228.00

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Brilliant Thallium Snapshot

$211.00

Sodium (Na⁺) in physiology

Sodium, along with potassium (K⁺), is one of the most important monovalent metal cations in living organisms. Sodium channels, Na⁺-permeable non-selective monovalent cation channels, and Na⁺ transporters play critical roles including modulating neuronal activity, powering transport of nutrients and signaling molecules, and regulating solute balance.

Na⁺-permeable channel and Na⁺ transporter-targeted drugs provide effective treatments for a diversity of indications: epilepsy, pain, bipolar disorder, depression, diuresis, and many others. An increasingly long list of Na⁺-permeable channels, and Na⁺ transporters are being associated with a wide variety of disorders. As a result, interest in Na⁺-permeable channels and Na⁺ transporters as drug targets remains high.

Because expanding our understanding of Na⁺ permeable channels and Na⁺ transporters are of such intense interest to both basic and drug discovery researchers, a facile means to measure their activity is required. Unfortunately, measuring intracellular and extracellular Na⁺ levels and dynamics using fluorescent indicators is challenging.

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

While ING-2 is an excellent Na⁺-sensitive, fluorescent indicator, the challenges of discriminating between K⁺ and Na⁺ are not trivial, and together with the often modest changes in intracellular Na⁺ results in relatively small signals compared to those observed with the Ca2⁺-sensitive fluorescent indicators.

In many instances, thallium flux offers an outstanding alternative to our Brilliant Sodium Assay. Our thallium flux assays take advantage of Tl⁺-selective fluorescent indicators, Thallos and Thallos Gold, and the fact that sodium channels and transporters readily accept Tl⁺ as a Na⁺ surrogate.

When Tl⁺ is added to the outside of cells loaded with thallium indicators, Tl⁺ entering cells through Na⁺ permeable channels and Na+ transporters results in a dramatic increase in fluorescence. Although the thallium assay is most commonly associated with high-throughput screening (HTS) of potassium channels, it is equally suitable for HTS of sodium channels and transporters.

Sodium channel assays using thallium flux

Brilliant Thallium

(EX 490 nm, EM 515 nm) High-throughput, no wash thallium flux assay. An optimal solution for measuring the activity of potassium channels and transporters, as well as sodium channels, non-selective cation channels, and G_i/o GPCRs.

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Brilliant Thallium Gold

(EX 530 nm, EM 550 nm) Brilliant Thallium Gold includes Thallos Gold – ION’s gold fluorescent thallium (Tl+) indicator. Red-shifted excitation and emission enable multiplexing with GFP-expressing cells or other green fluorescent indicators. Useful for fluorescence-based potassium channel assays and for studying a wide variety of monovalent cation channels (sodium channels), transporters, and GPCRs.

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Brilliant Thallium Snapshot

(EX 490 nm, EM 515 nm) An endpoint-compatible, 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 and transporters.

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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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Products	Excitation	Emission	Price	Quantity	Action
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.	530 nm	550 nm	$211.00 – $473.00	Brilliant Thallium Gold quantity	Clear Add to cart
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.	530 nm	550 nm	$211.00 – $473.00	Brilliant Thallium Gold Snapshot quantity	Clear Add to cart
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.	490 nm	515 nm	$211.00 – $473.00	Brilliant Thallium Snapshot quantity	Clear Add to cart
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.	490 nm	515 nm	$211.00 – $3,597.00	Brilliant Thallium quantity	Clear Add to cart
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.	525 nm	545 nm	$228.00 – $3,623.00	Brilliant Sodium Assays quantity	Clear Add to cart