Two Parameter Cytotoxicity Test Kits

IN CYTOTOX products are available worldwide

Extracellular LDH test principle

Cell death or cytotoxicity is classically evaluated by the quantification of plasma membrane damage. Lactate
dehydrogenase (LDH) is a stable cytoplasmic enzyme present in all cells, and is rapidly released into the cell
culture supernatant upon membrane damage or cell lysis. This assay is a fast and smageple method to determine
changes in the plasma membrane upon incubation with a test compound

LDH activity reduces pyruvate to lactate by oxidizing NADH to NAD+:



NADH degradation is measured spectrophotometrically by a decrease in the OD at 340 nm.

XTT test principle

Viable cells depend on an intact mitochondrial respiratory chain and an intact mitochondrial membrane. Toxic
agents can be identified using mitochondrial dehydrogenases from viable cells.

XTT (2,3-bis[2-methoxy-4-nitro-5-sulfopheny]-2H-tetrazolium-5-carboxyanilide inner salt) is a tetrazolium salt
that is cleaved to formazan by the succinate dehydrogenase system which belongs to the mitochondrial
respiratory chain, and is only active in viable cells. The mitochondrial succinate dehydrogenase reduces the
yellow tetrazolium salt into soluble orange formazan in the presence of an electron coupling reagent.

In contrast to the insoluble formazan salt crystals of MTT, XTT is converted to a water-soluble formazan product
without the need for a solubilization step prior spectrophotometric quantification. The enzyme activity is
measured at 480 nm (optimum) or at 450 nm.

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