PREEXPOSURE TEMPERATURE-ACCLIMATION AND DIET AS MODIFYING FACTORS FOR THE TOLERANCE OF GOLDEN IDE (LEUCISCUS-IDUS-MELANOTUS) TO SHORT-TERM EXPOSURE TO 4-CHLOROANILINE

The influence of different temperature and nutrition regimes on the acute toxicity of 4-chloroaniline to golden ide (Leuciscus idus melanotus) was investigated. Acute toxicity was determined over 48 hr at 20°C without feeding after a 2-day acclimation period. In an attempt to reveal underlying mechanisms accounting for diet- and temperature-related differences in the toxicant resistance of golden ide, biochemical and quantitative morphological parameters of the liver, a central organ in the xenobiotic metabolism of fish, were recorded throughout the 12-week acclimation period. In cold-acclimated fish, acute toxicity of 4-chloroaniline was 40% higher than in fish acclimated to 20°C. If compared to 20°C, preacclimation to 14°C was characterized by a lower specific growth rate, an increase of hepatic glycogen, and a decrease of body and liver lipid deposits. The organelle composition of hepatocytes was not significantly altered by temperature acclimation. For the nutrition experiment, commercially available diets A and B of similar crude composition were used. Acute toxicity of 4-chloroaniline was 60% lower with diet B than with diet A. If compared to diet B, diet A induced a higher specific growth rate and increased hepatocellular volume of endoplasmic reticulum and Golgi fields, whereas glycogen and lipid of the liver as well as body lipid contents were reduced. The toxicity of 4-chloroaniline was correlated with the development of the endoplasmic reticulum, the major site of biotransformation enzymes. A consistent correlation with lipid contents could not be established. Results illustrate not only that assay conditions during the actual test may profoundly interact with results of toxicity studies, but also that maintenance conditions before the test can have significant consequences on results. In order to improve reproducibility of the results of acute toxicity tests, more consideration should be given to the standardization of pretest maintenance conditions of fish. © 1992.