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DIETARY UPTAKE KINETICS OF 2,2', 5, 5'-TETRACHLOROBIPHENYL IN RAINBOW TROUT
Citation:
Nichols, J W., P N. Fitzsimmons, AND F W. Whiteman. DIETARY UPTAKE KINETICS OF 2,2', 5, 5'-TETRACHLOROBIPHENYL IN RAINBOW TROUT. DRUG METABOLISM AND DISPOSITION 29(7):1013-1022, (2001).
Description:
The disposition of 2,2',5,5'-tetrachlorobiphenyl (TCB) in rainbow trout (Oncorhynchus mykiss) was studied in dietary exposures with live prey. Trout were fed TCB-dosed fathead minnows (Pimephales promelas; 4% of body wt) containing whole-body residues of 244 (low dose) or 1663 (high dose) ng/g tissue (wet wt.) The GI ract was partitioned into the stomach, upper and lower intestine, and TCB concentrations were measured in gut contents and tissues, as well as other selected tissues. Gastric evacuation followed an exponential pattern and was 95% complete by 36 hr. TCB concentrations peaked at 12 hr in the upper intestinal tissues, 12-24 hr in blood, and 24 hr in stomach, lower intestine, muscle, liver and kidney tissues. The ratio of TCB in upper intestinal tissues to that in blood declined from 6 to 48 hr, as did the lumenal contents:tissue ratio. These observations are suggestive of an early liquid phase emptying of stomach contents to the upper intestine followed by rapid coassimilation of lipid and TCB. Tissue:blood concentration ratios for the stomach, lower intestine, muscle, liver, and kidney were constant and probably represented near equilibrium conditions. Fat:blood concentrations ratios increased through 96 hr suggesting that an equilibrium condition had not been attained and that TCB was redistirbuting to fat. TCB residues exhibited dose-dependency in all tissues except the upper intestine, and possibly also the liver. The cause of this lack of dose-dependence is unknown, but does not appear to be related to metabolic biotransformation. Peak chemical assimilation efficiencies of 94,5% (high dose) and 99.8% (low dose) were measured at 48 hr. Despite this high level of assimilation, however, TCB concentrations in feces were greater than expected.