Cell Proliferation and Cytotoxicity assays are commonly used in the drug discovery process to assess a compound’s ability to cause or block a biologic activity without having toxic effects on cells. Cytotoxicity assays are used in the study of tumor and viral cytolysis which can identify the precise and accurate quantification of cytotoxicity.

[3H] Thymidine assays are used to calculate cell proliferation to directly measure its incorporation in DNA. Radioactive labeled hormones are used to trace metabolic pathways and maintains natural biological function.

Chromium-51 (51Cr) release assays are used to determine the number of lymphocytes produced in response to infection or drug treatment.

Ion Flux Assays are used to directly access a functional change of ion channel activity. Radioactive isotopes are used to trace the cellular influx or efflux of specific ions, such as 22Na+, 45Ca2+ and 86Rb+, for the studies of Na+, Ca2+ and K+ channels, respectively. A commonly used assay is the 86Rb+ efflux for K+ channels or non-selective cation channels.