NARCOSIS DUE TO ENVIRONMENTAL-POLLUTANTS IN AQUATIC ORGANISMS - RESIDUE-BASED TOXICITY, MECHANISMS, AND MEMBRANE BURDENS

The well-known correlation between the hydrophobicity of narcotic chem icals and the exposure concentration needed to produce an effect indic ates that a lipid phase in the aquatic organism is the most likely tar get. The molar concentration in aquatic organisms at death is found to be approximately constant for different narcotic chemicals, varying f rom 2 to 8 mmol/kg organism. Because the proportion of lipid is known, the lethal in vivo membrane burden can be calculated to be 40 to 160 mmol/kg lipid. The exact mechanism underlying narcosis is still unknow n. However, disturbance by narcotic chemicals in model membrane system s has been investigated, attention having been paid to disturbance of phospholipids and proteins, and of the interaction between the two gro ups. Model membrane burdens of different chemicals have been shown to be approximately constant for a particular effect. Different effects a re found at different membrane concentrations. In the present review, the toxicity of narcotic chemicals to aquatic organisms is discussed, the possible mechanisms underlying narcosis are reviewed, and a compar ison is made between membrane burdens that are lethal in vivo and memb rane burdens that cause an effect in in vitro systems.