Evaluating the toxicity of Triton X-100 to protozoan, fish, and mammalian cells using fluorescent dyes as indicators of cell viability

Three viability assays using fluorescent dyes effectively detected a loss of viability in cultures of three mammalian cell lines (H4IIE, Caco2, and HepG-2), two fish cell lines (RTgill-W1 and RTL-W1), and a ciliated protozoan, Tetrahymena thermophila, after exposure to Triton X-100, used as a model toxicant. The dyes were Alamar Blue (AB), neutral red (NR), and propidium iodide, which respectively monitored energy metabolism, lysosomal activity, and membrane integrity. A fourth fluorescent dye, 5-carboxyfluorescein diacetate acetoxymethyl ester, was problematic. For 2-h Triton X-100 exposures, mammalian cell lines were as susceptible as piscine cell lines, whereas T thermophila was approximately twofold less sensitive as detected with AB and NR. Despite being less sensitive, cytotoxicity tests on T thermophila could be done in spring water which means that unlike animal cells they could be directly exposed to most industrial effluents without osmolality adjustments. Therefore, T thermophila could be a useful complement to animal cells as alternatives to fish in toxicity testing. (C) 2003 Elsevier Inc. All rights reserved.