Quantitative toxicity and population growth kinetics of Tetrahymena pyriformis exposed to selected polar narcotic and weak acid respiratory uncoupling phenols

Polar narcosis and weak acid respiratory uncoupling of oxidative phosphorylation are physical, reversible mechanisms of toxic action representing the narcoses mode of action. Both mechanisms are characterized by non-specific interactions at the membrane level of the cell. This study employs the freshwater ciliate, Tetrahymena pyriformis, as the test organism in order to quantitate the toxicity of phenols representing these two toxic mechanisms. High-quality quantitative structure-activity relationships based on the hydrophobicity of the toxicant were generated for each mechanism of action. In an attempt to correlate chronic toxicity with acute toxicity, acute-to-chronic ratios were generated for each mechanism. Acute-to-chronic ratios of 13.93 and 14.37 were generated for polar narcosis. Acute-to-chronic ratios of 8.01 and 12.00 were generated for weak acid respiratory uncouplers. Population growth kinetics were used to investigate the generation and lag times of T. pyriformis exposed to phenolic polar narcotics and weak acid uncouplers. Two trends in the growth kinetics were observed. The trend for polar narcotics was theorized to be dependent on the hydrophobicity of the molecule. The trend for weak acid respiratory uncouplers was theorized to be independent of hydrophobicity.