Ration and toxicant preexposure influence dieldrin accumulation by rainbow trout (<i>Salmo gairdneri</i>)

Abstract

Abstract Whole body accumulation and tissue distribution of dieldrin in rainbow trout were studied through oral-dose disposition tests and subchronic exposures via water (0.04 and 0.08 μg dieldrin/L) and/or diet (0.087 μg dieldrin/g fish/d). Growth and no-growth (maintenance) rations of 4 and 2% body weight per day were employed. In subchronic tests, apparent steady-state residue concentrations depended on ration and exposure concentration after 8 weeks of exposure. At 16 weeks, mean whole fish residue concentrations ranged from 120 to 1,400 ng dieldrin/g fish. Combination food and water exposures at a growth ration produced the highest accumulation values (1,300–1,400 ng dieldrin/g fish). Maintenance rations apparently limited accumulation to a maximum of 360 ng dieldrin/g fish. Whole body dieldrin concentration, calculated on the basis of total lipids, greatly reduced the differences in residue levels due to ration. Tissue distribution of a single oral dose of [14C]dieldrin was determined in naive (no pretreatment) fish and those preexposed via the diet for 2, 4 or 6 weeks. Tissue concentrations of the tracer dose were determined 48 h following administration. Retention of the [14C]dieldrin was similar in most tissues of naive, 2- or 6-week dieldrin-pretreated fish with a slight downward trend with duration of pretreatment. Retention of 14C in the bile of fish receiving maintenance and growth treatments increased two- and five-fold, respectively, in 6-week pretreated as compared with naive fish. After 4 weeks of pretreatment, 14C concentrations peaked in all tissues except the bile, gut, and gut contents.