Effects of an environmental estrogen, 17α-ethinyl-estradiol, on the maternal-fetal trophic relationship in the eelpout Zoarces viviparus (L)

In the present experiment pregnant eelpout Zoarces viviparus females were exposed to 0, 5, 10, 50, 500 ng/l of the synthetic estrogen ethinylestradiol (EE2) and to 500 ng/l estradiol-17β (E2) under flow-through conditions during 3 weeks and the maternal–fetal trophic response was investigated. The circulating yolk-precursor protein vitellogenin, measured by ELISA, increased from a mean control value of 0.017–36 mg/ml in the plasma of the motherfish exposed to the highest concentration of EE2. This increase in vitellogenin was also depicted by a 288% increase in circulating calcium levels. During pregnancy the ovary represents a new route of calcium loss from the maternal blood for the growth of the embryos. However, a significant decrease (120% in the group exposed to the highest concentration of EE2) in the calcium level in the ambient medium of the embryos, the ovarian fluid, was observed concomitant with the increase in maternal plasma calcium in the EE2-exposed females. In contrast, the level of circulating amino acids decreased in the maternal blood, with a slight concomitant increase in the ovarian fluid of the exposed fish. These and other metabolic observations indicate that exposure to different doses of EE2 and to estradiol-17β affects the maternal–fetal trophic relationship.