BIOTRANSFORMATION AND TISSUE DISTRIBUTION OF 1,2,3,7-TETRACHLORODIBENZO-PARA-DIOXIN, 1,2,3,4,7-PENTACHLORODIBENZO-PARA-DIOXIN AND 2,3,4,7,8-PENTACHLORODIBENZOFURAN IN RAINBOW-TROUT

Two polychlorinated dibenzo-p-dioxins were eliminated more slowly in rainbow trout which were treated with an inhibitor of biotransformation. Fish were given a single oral dose of either 14C-labeled 1,2,3,7-tetrachlorodibenzo-p-dioxin (T4CDD), 1,2,3,4,7-pentachlorodibenzo-p-dioxin (P5CDD) or 2,3,4,7,8-pentachlorodibenzofuran (P5CDF). Half of the fish were daily treated with piperonylbutoxide (PBO) which is a well known inhibitor of monooxygenase activity. The amounts of radioactivity were determined in liver, gall bladder, skin, muscle, spleen, heart, kidney, gills and intestine 2, 7, 14 and 21 days after administration. T4CDD and P5CDD were both eliminated more slowly in the PBO treated fish than in the fish which did not receive PBO. P5CDF showed no statistically different elimination rates in PBO treated and untreated fish. For all compounds the highest concentrations were found in liver and intestine. The highest absolute amounts of each compound was found in muscle. The slower elimination rates and the higher body burden of T4CDD and P5CDD in PBO treated trout indicate that biotransformation is very important for their elimination kinetics. Biotransformation may thus be responsible for the more rapid elimination and lower body burden of these compounds under normal conditions. © 1990.