COMPARATIVE EFFECTS OF THE WATER ACCOMMODATED FRACTION OF 3 OILS ON MUSSELS .3. QUANTITATIVE HISTOCHEMISTRY OF ENZYMES RELATED TO THE DETOXICATION METABOLISM

1. The reaction products derived from the histochemical demonstration of catalase and gamma-glutamyl transpeptidase (GGT) activities have been quantified in digestive tissue cells of mussels treated for 21, 49 and 91 days with the water accommodated fraction (WAF) of two different crude oils and of one commercial lubricant oil. 2. Although not in a dose-dependent manner, the mean absorbance of the catalase reaction product is significantly increased (up to 40% increases over control values) in digestive tubule cells after exposure to the 3 types of WAF. 3. These results could support the hypothesis that petroleum hydrocarbon toxicity is mediated in part by an increased generation of oxygen free radicals. 4. The elevation of catalase activity in digestive tubule cells could then represent an adaptative response that exerts a protective role against petroleum hydrocarbon-induced free radical toxicity. 5. Mean absorbance values of GGT, enzyme involved in phase II metabolism of electrophilic xenobiotics that catalyzes the second step of the mercapturic acid pathway, is transiently decreased under certain hydrocarbon exposure-conditions in both digestive tubule cells and stomach cells. 6. This reduction in GGT activity is discussed in relation with the overall effects of organic xenobiotics on mussel biotransformation enzymes.