Chronic Dieldrin Exposure Increases Hepatic Disposition and Biliary Excretion of [14C]Dieldrin in Rainbow Trout

Previous work demonstrated that exposure of laboratory animalsincluding fish to certain organochlorine (OC) insecticides alteredthe tissue distribution of a subsequent tracer dose of the same[¹⁴C]OC. In the present study, 10- to 20-g rainbow trout wereexposed to 15 ppm dieldrin in the diet. Fish were subsequentlychallenged at 2-week intervals with an intraperitoneal injectionof 0.1 mg/kg [¹⁴C]dieldrin and viscera (liver, bile, mesentericfat, kidney, and intestine) analyzed for radioactivity 24 hrlater. After 10 and 12 weeks of dieldrin pretreatment, [¹⁴C]-dieldrinwas significantly elevated relative to controls in liver (200%),bile (500%), and fat (500 and 1200% for 10 and 12 weeks, respectively)of pretreated fish. Other tissues were unchanged. Chloroform/methanolextractions revealed a time-dependent increase in label dispositionto carcass lipid in controls but not in pretreated fish. Altereddisposition could not be explained by changes in total bodylipid or induction of total cytochrome P-450 or ethoxyresorufin-0-deethylase,pentoxyreso-rufin-O-deethylase, glutathione S-transferase, orUDP glucuronosyltransferase activities. In vivo assessment of[¹⁴C]dieldrin metabolism revealed no increase in hepatic andonly a slight (22%) increase in biliary polannonpolar concentrationratio after 9 weeks 20 ppm dieldrin pretreatment. Results suggestthat constitutive changes in liver integral to dieldrin sequestration,transport, or excretion may be an adaptive response of troutto chronic OC exposure.