Effects of the Dioxin-like CB-126 on Metamorphosis and Stomach Development in Summer FlounderEPA Grant Number: U915748
Title: Effects of the Dioxin-like CB-126 on Metamorphosis and Stomach Development in Summer Flounder
Investigators: Soffientino, Bruno
Institution: University of Rhode Island
EPA Project Officer: Michaud, Jayne
Project Period: August 1, 2000 through August 1, 2003
Project Amount: $82,536
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Fellowship - Oceanography , Aquatic Ecosystems , Academic Fellowships
The objective of this project is to determine whether the dioxin-like CB-126 can affect metamorphosis and stomach development in summer flounder (Paralychthys dentatus) by disrupting thyroid hormone homeostasis.
The first set of experiments will address the overall sensitivity of metamorphosing larvae to polychlorinated biphenyls (PCBs) in terms of mortality; subsequently, a second set of experiments will examine sublethal developmental effects of PCBs (e.g., teratogenesis and structural deformities) using the stomach as the model organ. Finally, a third set of experiments will test the hypothesis that the observed effects are due to disruption of thyroid homeostasis. All experiments will employ CB-126, administered through the water, as the prototypical PCB because of its dioxin-like effects and mode of action. In the initial dose-response experiments, tritiated CB-126 will be used for accurate determination of the absorbed dose. Markers of cell proliferation and differentiation in the developing stomach mucosa will be used as endpoints of developmental disruption by PCBs. In addition, the temporal and spatial pattern of CYP1A1 immunostaining will be monitored as a marker of Aryl Hydrocarbon Receptor pathway activation. The Bromodeoxyuridine labeling index will be the marker for cell proliferation, while pepsinogen immunoreactivity and mucus-cell lectin-staining intensity will be the markers of cytodifferentiation. These endpoints were chosen because their changes depend on thyroid hormones and their developmental pattern is well known.
The results obtained in this work might become useful in risk assessment and possibly in the development of a bioassay for vertebrate developmental toxicity of PCBs. During preliminary experiments, a water-administered dose of 100 ng/l resulted in 100 percent mortality, making summer flounder larvae at least as sensitive as F. heteroclitus embryos to CB-126.