INDUCTION OF CYTOCHROME P4501A IN THE INTERTIDAL FISH ANOPLARCHUS-PURPURESCENS BY PRUDHOE BAY CRUDE-OIL AND ENVIRONMENTAL INDUCTION IN FISHFROM PRINCE-WILLIAM-SOUND

Cytochrome P4501A (CYP1A) induction is a sensitive and specific adapti ve response in fish exposed to xenobiotics including petroleum hydroca rbons. CYP1A expression was examined in the intertidal fish Anoplarchu s purpurescens collected from or caged at reference sites and sites oi led by the Exxon Valdez spill in Prince William Sound. Immunoblotting of hepatic microsomes showed that the content of CYP1A in fish at oile d sites was up to g-fold greater than that in reference site fish. Fis h injected with the CYP1A inducer beta-naphthoflavone showed a 70-fold induction of CYP1A, to levels six times the highest level seen in the field. To model the field exposure, fish were maintained over oiled s ediments and/or fed amphipods collected from an oiled site. Hepatic mi crosomal CYP1A was induced 49-fold in fish exposed to oiled sediments but rapidly returned to control levels after fish were removed from oi l exposure. Immunohistochemistry showed CYP1A induction in multiple or gans. CYP1A staining in hepatic and some extrahepatic cells was highly correlated (r(2) greater than or equal to 0.95) with the hepatic CYP1 A content detected by immunoblot. Oiled food induced CYP1A most strong ly in intestinal mucosal epithelial and endothelial cells. Relatively low levels of CYP1A were observed in liver, gill, and gonad of fish ex posed to oil through the diet, consistent with the metabolism of dieta ry hydrocarbons by intestinal CYP1A. Exposure to oiled sediment alone strongly induced CYP1A in endothelial cells in all organs examined. Th us, oil present in Prince William Sound sediments more than 1 year aft er the spill was able to induce CYP1A in intertidal fish. The caging a nd laboratory experiments indicate that the induction of CYP1A observe d in field specimens of A. purpurescens from oiled sites was due prima rily to persistent spill-derived hydrocarbons.