Choice and standardization of test protocols in cytotoxicology: A multicentre approach

A major problem that interferes with the introduction of in vitro tests for toxicological risk assessment is that of defining reliable standardized protocols. This issue was approached in the present study with an interlaboratory comparison of three cytotoxicity assays detecting chemical toxicity as impairment of cell viability in confluent cultures, reduction of colony forming ability, and inhibition of cell proliferation over 3 days of treatment. The study was performed using V79 cells, which are unable to activate indirectly-acting xenobiotics, and six chemicals with different mechanisms of action: two antioxidants (butylated hydroxyanisole and butylated hydroxytoluene), an inhibitor of protein synthesis (cycloheximide), an alkylating agent requiring metabolic activation (cyclophosphamide), an uncoupler of oxidative phosphorylation (dinitrophenol), and a genotoxic metal salt (potassium dichromate). The three tests produced the same rank of relative toxic potency for the tested chemicals, based on LC(50) values. The cell viability test appeared to be the most suited for the screening of unknown chemicals, given its simplicity and better reproducibility.