Microsomal enzyme activities, superoxide production, and antioxidant defenses in ribbed mussels ( Geukensia demissa) and wedge clams ( Rangia cuneata)

Abstract

1. 1. Microsomes of hepatopancreae from the ribbed mussel, Geukensia demissa, and the wedge clam, Rangia cuneata, were examined for their ability to catalyze the reduction/oxidation cycling of xenobiotics, particularly paraquat, and subsequently stimulate superoxide anion (O − 2) production. 2. 2. Levels of the microsomal electron transport components cytochrome P-450, cytochrome b 5, NADH-cytochrome c reductase, and NADPH-cytochrome c reductase were similar in both bivalves and like those seen in other species of molluscs. 3. 3. in vitro studies indicated a dose-dependent increase in the rate of O − 2 generated in microsomal fractions incubated with paraquat; the highest concentration of paraquat employed (4 mM) elicited an 81% increase in cytochrome c reduction in mussels and a 135% increase in clams. In both species, cytochrome c reduction was inhibited by the addition of exogenous superoxide dismutase (SOD). 4. 4. Activities of SOD and catalase and the concentration of reduced glutathione were determined in the hepatopancreas of these bivalves. Similar values for these antioxidants were observed in both species.