Seasonal responses to diesel oil and subsequent recovery of the cytocgrome P-450 monooxygenase system in the common mussel, Mytilus edulis L., and the periwinkle, Littorina littorea L

Abstract

Mussels and periwinkles under natural environmental conditions were exposed long-term (4–8 and 16–24 months, respectively) to environmentally realistic levels of, on average, 30 and 129 ppb diesel oil and then allowed to recover for 2–9 months in the absence of oil. With oil exposure, increases were seen in digestive gland microsomal cytochrome P-450 content and NADPH-cytochrome c reductase activity, and the changes in the latter were particularly consistent in periwinkles, showing a stepwise elevation with oil dosage at all times of the year. The changes were less consistent in mussels, with a dependence on season or reproductive condition being indicated. Fewer changes were seen in cytochrome b 5 content and the associated NADH-dependent reductase activities of the digestive gland microsomes of both molluscs. The microsomal parameters tended to be higher in female than male mussels, but the responses of the sexes to oil-exposure were not obviously different. With recovery the elevated microsomal parameters declined and the changes paralleled the depuration of polynuclear aromatic hydrocarbons from the tissues. Few changes were seen in benzo[ a]pyrene hydroxylase activity. It is concluded that some of the observed enzyme changes, particularly in periwinkles, could have a potential for application in pollution monitoring, but that the in vivo function of these enzymes must first be elucidated.