John Wiley & Sons, Ltd.

The effects of an environmentally relevant 58 congener polychlorinated biphenyl (PCB) mixture on cardiac development in the chick embryo

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Chicken (Gallus domesticus) embryonic exposure in ovo to a 58 congener PCB mixture resulted in teratogenic heart defects in chick embryos at critical heart developmental stages Hamburger Hamiltion (HH) 10, 16, and 20. The 58 congener mixture contained relative proportions of primary congeners measured in belted sandpiper (Megaceryle alcyon) and spotted sandpiper (Actitis macularia) eggs collected along the upper Hudson River, NY, and chicken doses were well below observed environmental exposure levels. Embryos were injected with 0.08 µg PCBs/g egg wt and 0.50 µg PCBs/g egg wt (0.01 and 0.064 ng TEQ/g, respectively) at embryonic day 0, prior to incubation. Mortality of exposed embryos was increased at all developmental stages, with a marked rise in cardiomyopathies at HH16 and HH20 (p<0.05). Heart abnormalities occurred across all treatments, including abnormal elongation and expansion of the heart tube at HH10, improper looping and orientation, indentations in the emerging ventricular wall (HH16, HH20), and irregularities in overall heart shape (HH10, HH16, HH20). Histology was conducted on two cardiac proteins critical to embryonic heart development, ventricular myosin heavy chain (VMHC) and titin, to investigate potential mechanistic effects of PCBs on heart development, but no difference was observed in spatio‐temporal expression. Similarly, cellular apoptosis in the developing heart was not affected by exposure to the PCB mixture. Conversely, cardiomyocyte proliferation rates dramatically declined (p<0.01) at HH16 and HH20 as PCB exposure concentrations increased. Early embryonic cardiomyocyte proliferation contributes to proper formation of the morphology and overall thickness of the ventricular wall. Therefore, in ovo exposure to this 58 congener PCB mixture at critical stages adversely affects embryonic heart development. Environ. Toxicol. Chem. © 2013 SETAC

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