A single i.p. injection of 5 pg 3,3',4,4'-tetrachlorobiphenyl (TCBP)/g body mass in adult brook trout (IFkB&ve&inus fontinadis) resulted in decreased (p < 0.0001) growth rate despite pair feeding. Plasma retinol decreased (p < 0.0037). Intestinal retinyl palmitate (RP) and 3,4-dehydroretinyl palmitate (DRP) concentrations decreased in TCBP-injected males (RP, p < 0.0143; DWP, p < 0.0009), whereas retinoid levels did mot decrease significantly in TCBP-injected females. The RP:DRP ratio in trout liver increased (p < O.OOOl)B These results suggested that DRB is more sensitive than RP to the effects of K B P . No significant differences in ovarian retinoids occurred in post-spawning trout. Field validation of the effects on intestinal retinoids was conducted with lake sturgeon (Aeipenserfudveseens) caught at a contaminated site on the Des Prairies River wear MontrCal (Strn Lawrence River population) and reference sturgeon taken from a site near the origin of the Ottawa River in Laverendrye Park. Intestinal retinoid concentrations were lower (RP, p < 0.0008; DWP, p < 0.0004) in the St. Lawrence River sturgeon.Our results demonstrate that a coplanar PCB is capable of altering vitamin A dynamics in several tissues and organs, and may cause a lowering of retinoids in the intestine.RCsamC : Ume injection i.p. de 3,3',4,4'-tCtrachlorobiphCnyle (TCBP), 5 pg/g de poids corporel, a entrain6 une rCductiom (p < 0.0001) du taux de croissance chez 190mble de fontaine (Salvelinus fonbina&is), malgrC le fait que les groupes tCmoins et traitCs avaient consommC la mCme quantitC de noun-iture par p.c. Le rktinol plasmatique a diminuC (p < 0,0037). Les niveaux de palmitate de rCtinol (RP) et de 3,4-dCshydrorCtiny% palmitate (DRP) dans %es intestins des miiles traitCs ont diminuC (RP, p < 0,0143; DRP, p < 00,0009), contrairement aux femelles tmitCes dont les niveaux de rCtinoi'des n90nt pas diminuC. Le rapport RP:DRP dans le foie a augment6 (p < 0,0001). Ces rCsultats suggkrent que le DRP est plus sensible que le RP quant aux effets du TCBP. Les concentrations des rCtino'ides ovariens n'ont pas Ct C affectCes. Les effets du TCBP sur les rCtino'ides intestinaux ont fait l'objet dkne validation sur le terrain avec les estuageons jaunes (AcipenserfuIvescens) captures dans un site contamin6 de la aivikre des Prairies, pr$s de MontrCal (population du fleuve Saint-Laurent), et dans un site rkfbrence sur la rivi6re des Outaouais, dam le parc LaVCrendrye. Les concentrations des rCtinoYdes iwtestinaux Ctaient plus faibles (RP, p < 0,0808; DRP, p < 0,0004) chez les esturgeons du site contaxnine. Nos rCsultats dCmontrent la capacitC d'un BPC coplane d'affecter la dynamique de la vitamine A dans plusieurs tissus et organes, entre autres les intestins.A. Ndayibagira, Me-J. ClouUiere Labsratoire TOXEN and DCpartement des Sciences biologiques,

Since the early 1990s, a substantial number of deformed frogs have been observed in North America, particularly in the upper Midwest and Canada. Attempts to understand the etiology of the deformed frog problem have met with limited success to date with nearly as many proposed explanations as research groups working on the problem. Models for the mechanism underlying the development of deformed frogs include parasite/predation, ultraviolet radiation, and chemical exposure. Each model has its strengths and weaknesses. Despite contentious debate among researchers, there is an overall consensus that the increasing prevalence of deformed frogs is the result of a water-borne contaminant that has recently appeared, or reached a critical concentration. Our detailed analysis of malformed frogs collected in Minnesota ponds and lakes suggested that limb patterning was being modified by the disruption of a retinoid-sensitive developmental signaling pathway. Accordingly, we focused in the identification and characterization of bioactive retinoids from lake water and showed that retinoid treatment of frog embryos at sensitive times of development could recapitulate the full spectrum of limb abnormalities observed in field specimens in the laboratory. These data have led to the conclusion that inappropriate modulation of retinoid signaling by environmental contaminants is the mechanism underlying the increased incidence of frog malformations.

Extremely low stores of vitamin A have been reported in fish and birds inhabiting regions contaminated by coplanar polychlorinated biphenyls (PCBs) and other organochlorines, suggesting many possible effects on retinoid biochemical pathways. Metabolic imbalances associated with biologically active retinoids (e.g., retinoic acid) could be associated with teratogenesis, edema, growth inhibition, reproductive impairment, immunosuppression, and susceptibility to cancer. Sexually mature brook trout were injected intraperitoneally with the coplanar PCB 3,3Ј,4,4Ј-tetrachlorobiphenyl (TCBP) and again 4 weeks later. At 8 weeks, retinoic acid metabolism was measured in liver microsomes. To our knowledge, retinoic acid conjugation by UDP-glucuronyltransferase is described here for the first time in fish. A substantial rate of glucuronidation was detected in the microsomes from control brook trout, which tended to increase over the dose range of TCBP. Glucuronidation was significantly greater in fish receiving the 10 g/ g body weight dose level. Metabolism through the cytochrome P450 system was also dose-dependent, resulting in significantly greater production of 4-hydroxyretinoic acid at the 10 g/g dose level. In contrast, subsequent oxidation to 4-oxo-retinoic acid was greatest at the 1 g/g dose level and did not increase further at higher doses. Liver stores of dehydroretinyl palmitate/oleate were significantly decreased at the 5 and 10 g/g dose levels.

No abstract

No abstract