BIOASSAY TECHNIQUE USING NONSPECIFIC ESTERASE-ACTIVITIES OF TETRAHYMENA-PYRIFORMIS FOR SCREENING AND ASSESSING CYTOTOXICITY OF XENOBIOTICS

A simple and rapid test for screening and assessing the cytotoxicity o f xenobiotics was developed with Tetrahymena pyriformis. The method es timates the activities of nonspecific esterases of a cell by concentra ting within it a specific amount of fluorescence associated with fluor escein dye. The 1-h median effective concentration (EC50) values of 10 inorganic and eight organic substances are presented and compared to those of three other bioassays: the conventional T. pyriformis prolife ration rate 9-h median inhibitory concentrations, the Microtox(R) 30-m in EC50s, and the Daphnia magna 4-methylumbelliferyl beta-D galactosid e 1-h EC50s. A highly significant correlation was found between the re sults obtained with the fluorescein diacetate test and those obtained with the growth inhibition and Microtox tests. This in vivo enzymatic test showed high sensitivity to all compounds tested except Cr6+ and s odium dodecyl sulfate.