ASSOCIATION OF MERCURY AND SELENIUM WITH ALTERED GLUTATHIONE METABOLISM AND OXIDATIVE STRESS IN DIVING DUCKS FROM THE SAN-FRANCISCO BAY-REGION, USA

Adult male greater scaup (Aythya marila), surf scoters (Melanitta pers picillata), and ruddy ducks (Oxyura jamaicensis) were collected from S uisun Bay and coastal Tomales Bay in the greater San Francisco Bay are a to assess exposure to inorganic contaminants. Hepatic Se concentrati ons were highest in greater scaup (geometric mean = 67 ppm dry weight) and surf scoters (119 ppm) in Suisun Bay, whereas hepatic Hg was high est (19 ppm) in greater scaup and surf scoters from Tomales Bay. Hepat ic Se and Hg were lower in ruddy ducks and did not differ between loca tions. Hepatic supernatants were assayed for enzymes related to glutat hione metabolism and antioxidant activity, including glucose-6-phospha te dehydrogenase (G-6-PDH), glutathione peroxidase (GSH peroxidase), g lutathione reductase (GSSG reductase), and glutathione-S-transferase ( GSH transferase). Glutathione peroxidase activity was higher in surf s coters and ruddy ducks, and G-6-PDH was higher in greater scaup and su rf scoters from Suisun Bay than Tomales Bay. Glutathione reductase (GS SG) was higher in SS from Suisun Bay. The ratio of oxidized glutathion e (GSSG) to reduced glutathione (GSH) was greater in all species from Tomales Bay. The following significant relationships were found in one or more species with increasing hepatic Hg concentration: lower body, liver, and heart weights; decreased hepatic GSH concentration and G-6 -PDH and GSH peroxidase activities; increased ratio of GSSG to GSH; an d increased GSSG reductase activity. With increasing hepatic Se concen tration, GSH peroxidase increased, but GSH decreased. It is concluded that measurement of associated enzymes in conjunction with thiol statu s may be a useful bioindicator to discriminate between Hg and Se effec ts. Concentrations of Hg and Se and the above variables affected have been associated with adverse effects on reproduction and neurological function in experimental studies with mallards.