Comparisons of toxicities elicited by nonpolar and polar narcotics, weak acid 
uncouplers of oxidative phosphorylation, and bioreactive chemicals between the 
eucaryotic systems Pimephales promelas and Tetrahymena pyriformis and the 
procaryotic systems Escherichia coli and Photobacterium phosphoreum were 
performed. Each chemical had been a priori assigned a mechanism/mode of action 
based on the results from previous studies with eucaryotic systems. 
Hydrophobicity-dependent QSARs for nonpolar narcosis for both the E. coli and 
the P. phosphoreum endpoints was developed. However, due to the lack of a 
significant relationship between P. phosphoreum toxicity and log Kow, such a 
QSAR for polar narcosis was developed only for the E. coli endpoint. Except for 
4-nitroaniline (the only chemical in the examined group that required activation 
to become the Michael receptor), all chemicals containing reactive substructures 
revealed excess toxicity over polar narcosis QSAR for E. coli endpoints. 
Moreover, chloroacidic acid and ethyl chloroacetate in this system also appear 
to be bioreactive. The only mechanism that seemed to not exist in the 
procaryotic system was uncoupling of oxidative phosphorylation. Chemicals from 
this group, except 2,4-dinitroaniline, did not exhibit excess toxicity over 
polar narcosis QSAR. This was thought to be explained by the lack of 
mitochondria in procaryotes, the target site of uncoupling agents in eucaryotes. 
In addition, evaluation of toxicities of halogen-substituted short-chain 
carboxylic alcohols indicated that their mechanisms vary, depending upon the 
type of substitution and the system.