Two Parameter Cytotoxicity Test Kits

IN CYTOTOX products are available worldwide

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.

PAC test principle

The acid phosphatase (PAC) is a hydrolase with a pH optimum below 7 and catalyzes the dephosphorylation of organic ortho-phosphoric esters. The enzyme has transferase activity leading to the fixation of a phosphate to the hydroxyl group of an alcohol. PAC is located in the golgi apparatus and therefore a marker for lysosomal activity.

The membrane associated PAC cleaves the colorless substrate p-nitrophenyl phosphate to the colorless pnitrophenol which is measured spectrophotometrically at 405 nm after conversion to the yellow p-nitrophenolate form by addition of 1 M NaOH.An increase or decrease in cell numbers results in a concomitant increase or decrease in the amount of substrate converted by the test compound.

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