QUANTITATIVE STRUCTURE-ACTIVITY-RELATIONSHIPS OF CHEMICALS ACTING BY NONPOLAR NARCOSIS - THEORETICAL CONSIDERATIONS

Theoretical quantitative structure-activity relationships have been es tablished based on narcotic mechanisms of action and toxicity data to the fathead minnow, Daphnia magna and Vibrio fischeri. The results con firmed that hydrophobicity is important in modelling narcosis. However , the results of the present investigation also confirmed that molecul ar bulk may play an important role in toxicity to aqueous organisms, e specially in the toxicity to organisms with lower lipid content, for e xample, V. fischeri. The results are discussed in the light of other i nter-species differences that may occur as a consequence of accumulati on and clearance kinetics and the relative metabolism of xenobiotics b y each organism. Because of the complex tissue structure of organisms, classification of narcotic compounds using hydrophobicity parameters alone can sometimes lead to errors.