Adrenocortical function and hepatic naphthalene metabolism in mallard ducks ( Anas platyrhynchos) consuming petroleum distillates

The reductions in plasma corticosterone concentration and the increases in hepatic naphthalene-metabolizing activity that occur when mallard ducks are acutely exposed to petroleum-contaminated food are each caused by distinct molecular-size classes of compounds in the whole crude oil. The decrease in plasma corticosterone concentration only occurred in birds given food contaminated with proportionate volumes of distillation fractions with boiling point ranges of X to 205°C and 205 to 399°C. Significant increases in total hepatic naphthalene-metabolizing activity, however, were only induced when birds were given food containing distillation fractions with boiling point ranges of 205 to 399°C and 399 to 482°C. The residual material containing compounds with boiling points in excess of 482°C had no effect on either plasma corticosterone concentration or hepatic naphthalene metabolism. Although the combined effects of the two distillation fractions that affected plasma corticosterone were approximately equal to that of the whole crude oil, the combined effects of the fractions that induced increases in hepatic naphthalene metabolism were almost twice that of the crude oil. Also, the relative abundances of the four distillation fractions were not the same and differences between their toxic potencies were identified with respect to both physiological parameters.