Dietary accumulation and biochemical responses of juvenile rainbow trout (Oncorhynchus mykiss) to 3,3',4,4',5-pentachlorobiphenyl (PCB 126).
Juvenile rainbow trout (Oncorhynchus mykiss) (initial weights 2-5 g) were exposed to three dietary concentrations (0, 12.4 and 126 ng g(-1), wet weight) of a 14C-labelled 3,3',4,4',5-pentachlorobiphenyl (PCB 126) for 30 days followed by 160 days of clean food. We assessed bioaccumulation, histology (liver and thyroid) and biochemical responses (liver ethoxyresorufin-O-deethylase (EROD), liver vitamins (retinoids and tocopherol) and muscle thyroid hormone levels) along with growth and survival. The half-life of PCB 126 in the rainbow trout ranged from 82 to 180 days while biomagnification factors (BMF) ranged from 2.5 to 4.1 providing further evidence that PCB 126 is among the most bioaccumulative PCB congeners. Toluene extractable 14C declined with time in the trout suggesting the possibility of some biotransformation and/or covalent bonding with biological macromolecules. The threshold for liver EROD induction by PCB 126 was approximately 0.1 ng g(-1) (wet weight). EROD activities in the low- and high treatments were 9 and 44 times greater than control, respectively, and remained elevated throughout the experiment. EROD activity was correlated with whole body concentrations of PCB 126 although there was evidence of EROD activity suppression in the highly exposed fish. Liver didehydroretinoids and tocopherol concentrations were depressed by the high PCB 126 dose after 30 days exposure. Initially, muscle concentrations of thyroxine (T4) and triiodo-L-thyronine (T3) declined as the fish grew during the experiment, and exposure to PCB 126 accelerated the growth related decline. More information is needed to assess the functional significance of the reduced muscular stores of thyroid hormones. Despite the changes in liver EROD, liver vitamins and muscle thyroid hormones, liver and thyroid histology in trout examined after 30 days exposure and growth parameters were unaffected by PCB 126. This indicates that the functional competences of the physiological factors associated with growth were maintained under the experimental conditions.
Environment Canada, National Water Research Institute, 867 Lakeshore Blvd., PO Box 5050, Ont., L7R 4A6, Burlington, Canada. scott.brown@cciw.ca
Scott B
SB
Brown
Aaron T
AT
Fisk
Mitra
M
Brown
Maria
M
Villella
Derek C G
DC
Muir
Robert E
RE
Evans
W Lyle
WL
Lockhart
Donald A
DA
Metner
H Megan
HM
Cooley
D000818:Animals; D002250:Carbon Radioisotopes; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004965:Estrogen Antagonists / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006207:Half-Life; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006899:Mixed Function Oxygenases / Q000096:biosynthesis; D017686:Oncorhynchus mykiss / Q000254:growth & development / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D011078:Polychlorinated Biphenyls / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013963:Thyroid Hormones / Q000378:metabolism; D014018:Tissue Distribution; D014874:Water Pollutants, Chemical / Q000008:administration & dosage / Q000493:pharmacokinetics*
D002250:Carbon Radioisotopes; D004965:Estrogen Antagonists; D013963:Thyroid Hormones; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls; D006899:Mixed Function Oxygenases; D019363:Cytochrome P-450 CYP1A1; C023035:3,4,5,3',4'-pentachlorobiphenyl