Cell-Based Assays

Cellular Uptake Assay

Cell-based uptake assays can be used to measure either the transport or internalization of labeled compounds into cells or the potency of unlabled test compounds in inhibiting this transport.  Labeled substances can be neurotransmitters, metabolites, drugs or proteins.  Applications include:

• Determination of IC₅₀ values for test compounds against cellular uptake of radiolabeled neurotransmitters.
• Determination of IC₅₀ values for test compounds against uptake of tritium or ¹⁴C-labeled metabolites or drugs.
• Cellular uptake and internalization of ¹²⁵I-labeled proteins.

Release Assays

Radiometric release assays can be used to quantify the efflux of labeled substances from cells.  Efflux can be via membrane ion channels, membrane transport or from cell lysis.  Applications include:

• ⁸⁶Rb⁺ rubidium efflux assay for quantification of drug effects on stimulation or inhibition of  ligand-gated ion channel activity (nicotinic).
• Efflux or release of ³H and ¹²⁵I-labeled drugs or proteins from cells.
• ⁵¹Cr chromium release assay for quantification of cell-mediated cytotoxicity.

 

Examples

Fig 1.

Inhibition of [³H]dopamine uptake into rat brain synaptosomes by the dopamine transport inhibitors, GBR 12909 and cocaine (left panel), shown in comparison with inhibition of [³H]mazindol binding (right panel).

Fig 2.

Stimulation of ⁸⁶Rb⁺ efflux from SH-SY5Y cells by the nicotinic receptor agonists, epibatidine and nicotine

Fig 3.

Loss of ¹²⁵I-labeled trastuzimab from SKBr3 cells, following addition of a saturating concentration of unlabelled antibody to the medium