LAUSR

Cell exposure to cytotoxic substrates can cause decreased cell viability or cellular death through necrosis or apoptosis. The common characteristic of both reaction patterns (necrosis and apoptosis) is a compromised or damaged cell membrane, which results in a release of the cytoplasmatic enzyme lactate dehydrogenase (LDH) into the extracellular space. For this reason the content of this enzyme in the supernatants from cells can be used as an indicator of damaged cell membrane integrity and serve as a general means to assess cell viability by measuring plasma membrane permeability. However, cell culture media which are used to maintain and to support cell growth commonly need serum supplementation, and sera already contain various LDH amounts, which may increase background absorbance in LDH release assays. Additionally the serum content varies depending on the cellular needs. For this reasons we tested the effect of different serum loads (inactivated fetal bovine serum [FBS]; 1–10 vol%) on the results of a commercially available LDH release assay (Cytotoxicity detection Kit, Roche) using 3T3 cells. An FBS concentration of 1 vol% was found to still maintain 3T3 cell viability, and after cell exposure to a cytotoxic substrate (surfactant) the cellular LDH release was higher than in the cells which were grown with higher serum concentrations (5 and 10 vol%). These results show that a serum content of 1 vol% is advantageous for cytotoxicity assays based on the LDH release, but due to the cellular differences in the need of serum components test results are limited to 3T3 cells.