DISPOSITION AND METABOLISM OF 2,3,7,8-TETRACHLORODIBENZOFURAN BY RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The disposition and metabolism of 2,3,7,8-tetrachlorodibenzofuran (TCD F) was investigated in rainbow trout (Oncorhynchus mykiss) in order to better understand the metabolic and physiological factors that modula te the fate of this extremely toxic compound in rainbow trout compared to other species. The fish were dosed orally with [H-3]TCDF (1 mu g/k g); fish were terminated at 1-19 days for the determination of whole b ody half-life or at 0.3-28 days for determination of tissue distributi on. Unassimilated TCDF (51.5% of the dose) was eliminated with a half- life of 0.84 days. The assimilated body burden of TCDF equivalents dec reased with a half-life of 14.8 days (determined between 3 and 19 days ). Trout muscle showed a relatively high capacity to accumulate and re tain (unmetabolized) TCDF, accounting, at 3 days, for 32% of the body burden of TCDF equivalents (half-life in muscle, 15.2 days). Trout liv er, on the other hand, showed a relatively low capacity to accumulate and metabolize TCDF. At 3 days, the concentrations of TCDF equivalents in liver and bile were, respectively, 0.37 ng/g liver (0.88% of the b ody burden) and 4.8 ng/ml bile. The data suggest that the relatively h igh affinity of lipid-rich trout muscle for TCDF limits the ability of the liver to accumulate and metabolize TCDF. The major TCDF metabolit es found in trout liver and bile were, respectively, 4-OH-TCDF and TCD F-4-O-glucuronide. (C) 1996 Academic Press, Inc.