Measurement of intracellular LDH activity in 96-well cultures: A rapid and automated assay for cytotoxicity studies

Summary The present paper describes a rapid, easy, sensitive, and automated spectrophotometric assay for intracellular lactate dehydrogenase (LDH) measurement in 96-well plates of adherent cells for cytotoxicity studies. The procedure involves “in situ” homogenization of cells, followed by measurement of LDH activity with a colorimetric method based on the reduction of a tetrazolium salt to a violet formazan by the NADH formed by LDH. Color intensity can be measured in conventional ELISA readers, and the data can be fed to an “on line” computer for rapid processing. The color absorbance measured is time- and enzyme-concentration dependent. LDH activity measured with this micromethod is coincident with that measured in larger culture plates after individual homogenization and conventional LDH measurement. The advantages of this method are the smaller number of cells required, easy automation, drastic reduction of time for processing individual wells, and the possibility of examining multiple variables in the same experiment.