Gestational and lactational exposure to the polychlorinated biphenyl mixture Aroclor 1254 modulates retinoid homeostasis in rat offspring.

Polychlorinated biphenyls (PCBs) induce a broad spectrum of biochemical and toxic effects in mammals including alterations of the vital retinoid (vitamin A) system. The aim of this study was to characterize alterations of tissue retinoid levels in rat offspring and their dams following gestational and lactational exposure to the PCB mixture Aroclor 1254 (A1254) and to assess the interrelationship of these changes with other established sensitive biochemical and toxicological endpoints. Sprague-Dawley rat dams were exposed orally to 0 or 15 mg/kg body weight/day of A1254 from gestational day 1 to postnatal day (PND) 23. Livers, kidneys and serum were collected from the offspring on PNDs 35, 77 and 350. Tissue and serum retinoid levels, hepatic cytochrome P450 (CYP) enzymes and serum thyroid hormones were analyzed. A multivariate regression between A1254 treatment, hepatic retinoid levels, hepatic CYP enzymes activities, thyroid hormone levels and body/liver weights was performed using an orthogonal partial least-squares (PLS) analysis. The contribution of dioxin-like (DL) components of A1254 to the observed effects was also estimated using the toxic equivalency (TEQ) concept. In both male and female offspring short-term alterations in tissue retinoid levels occurred at PND35, i.e. decreased levels of hepatic retinol and retinoic acid (RA) metabolite 9-cis-4-oxo-13,14-dihydro-RA with concurrent increases in hepatic and renal all-trans-RA levels. Long-term changes consisted of decreased hepatic retinyl palmitate and increased renal retinol levels that were apparent until PND350. Retinoid system alterations were associated with altered CYP enzyme activities and serum thyroid hormone levels as well as body and liver weights in both offspring and dams. The estimated DL activity was within an order of magnitude of the theoretical TEQ for different endpoints, indicating significant involvement of DL congeners in the observed effects. This study shows that tissue retinoid levels are affected both short- and long-term by developmental A1254 exposure and are associated with alterations of other established endpoints of toxicological concern.

Esteban J ，Elabbas LE ，Borg D ，Herlin M ，Åkesson A ，Barber X ，Hamscher G ，Nau H ，Bowers WJ ，Nakai JS ，Viluksela M ，Håkansson H ... -  《-》

In utero and lactational exposure to a mixture of environmental contaminants detected in Canadian Arctic human populations alters retinoid levels in rat offspring with low margins of exposure.

Elabbas LE ，Esteban J ，Barber X ，Hamscher G ，Nau H ，Bowers WJ ，Nakai JS ，Herlin M ，Åkesson A ，Viluksela M ，Borg D ，Håkansson H ... -  《-》

Fetal, neonatal, and long-term alterations in hepatic retinoid levels following maternal polychlorinated biphenyl exposure in rats.

Morse DC ，Brouwer A 《TOXICOLOGY AND APPLIED PHARMACOLOGY》

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) alters the endogenous metabolism of all-trans-retinoic acid in the rat.

Schmidt CK ，Hoegberg P ，Fletcher N ，Nilsson CB ，Trossvik C ，Håkansson H ，Nau H ... -  《ARCHIVES OF TOXICOLOGY》

In utero and lactational exposure to Aroclor 1254 affects bone geometry, mineral density and biomechanical properties of rat offspring.

Exposure to polychlorinated biphenyls (PCBs) induce a broad spectrum of toxic effects in various organs including bone. The most susceptible age-groups to the toxic effects of PCBs are foetuses and infants. The aim of the present study was to quantitatively evaluate changes in bone geometry, mineral density and biomechanical properties following perinatal exposure to the PCB mixture, Aroclor 1254 (A1254), and to examine the persistence of observed bone alterations by following the offspring over time. Sprague-Dawley rat offspring were exposed to A1254 from gestational day 1 to post-natal day (PND) 23. Femur and tibia were collected on PNDs 35, 77 and 350 and were analyzed by peripheral quantitative computed tomography and biomechanical testing. At PND35, exposure to A1254 induced short, thin femur and tibia, with reduced mechanical strength of femoral neck. No treatment-related bone changes were detected in offspring at PND77 or PND350. In conclusion, the present investigation suggests that perinatal exposure to A1254 leads to shorter, thinner and weaker bones in juvenile rats at PND35, with these effects being absent at later time-points as exposure is discontinued. The results indicate that the observed bone effects are mainly driven by the dioxin-like congeners, although it cannot exclude the contribution of the non dioxin-like congeners to the exposure outcome.

Elabbas LE ，Herlin M ，Finnilä MA ，Rendel F ，Stern N ，Trossvik C ，Bowers WJ ，Nakai J ，Tuukkanen J ，Viluksela M ，Heimeier RA ，Akesson A ，Håkansson H ... -  《-》