Abstract
The disposition of [UL-14C]2,2′,5,5′-tetrachlorobiphenyl (TCB) in rainbow trout (Oncorhynchus mykiss) was studied in acute dietary exposures using TCB-contaminated fathead minnows (Pimephales promelas). Trout were sampled at several postfeeding time points and TCB-derived radioactivity was measured in gut contents and selected tissues. Gastric evacuation was exponential with time and was 95% complete within 36 h of feeding. The ratio of activity in upper intestinal tissue to that in blood declined between 6 and 48 h, as did the lumenal contents/tissue ratio. Stomach content lipid declined between 0 and 24 h, while the lipid content of chyme remained relatively constant. These observations are consistent with liquid phase emptying of lipid and TCB to the upper intestine followed by rapid coassimilation. Tissue/blood activity ratios for the stomach, lower intestine, muscle, liver, and kidney were constant and probably represented near equilibrium conditions. The fat/blood activity ratio increased through 96 h, indicating that TCB was redistributing to fat. The lower intestinal tissue/feces activity ratio increased between 6 and 24 h and then declined rapidly. Fecal lipid content also increased between 6 and 24 h, but the amount of this increase was insufficient to explain observed changes in the distribution of TCB-derived activity. A small amount of 3-hydroxy TCB was detected in feces. Generally, however, metabolism had little or no impact on the uptake, distribution or elimination of TCB. Measured assimilation efficiencies exceeded 90% and are the highest ever reported in fish feeding studies with TCB.
Footnotes
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This manuscript was reviewed in accordance with official EPA policy. Mention of any trade names does not constitute endorsement by EPA or the Federal Government.
- Abbreviations used are::
- log KOW
- log of a compound's octanol/water partition coefficient
- GI
- gastrointestinal
- TCB
- 2,2′,5,5′-tetrachlorobiphenyl
- LSC
- liquid scintillation counting
- GC/MS
- gas chromatography/mass spectrometry
- HCB
- hexachlorobenzene
- Received December 13, 2000.
- Accepted March 15, 2001.
- The American Society for Pharmacology and Experimental Therapeutics
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