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RELATIONSHIP BETWEEN PHYSIOLOGICAL RESPONSES AND REPRODUCTIVE IMPAIRMENT IN JAPANESE MEDAKA (ORYZIAS LATIPES): EFFECTS OF ETHINYLESTRADIOL
Citation:
Thompson, S. C., C M. Foran, AND W H. Benson. RELATIONSHIP BETWEEN PHYSIOLOGICAL RESPONSES AND REPRODUCTIVE IMPAIRMENT IN JAPANESE MEDAKA (ORYZIAS LATIPES): EFFECTS OF ETHINYLESTRADIOL. Presented at 21st Annual Meeting of the Society of Environmental Toxicology and Chemistry, Nashville, TN, 12-16 November 2000.
Description:
Previous studies have measured various physiological responses in fish from exposure to endocrine disrupting compounds, while others have observed higher level effects on reproduction and development. However, little is understood about the relationship that might exist between altered endocrine function and the consequences for future generations. This is primarily because methods used to measure responses along the hypothalamus-pituitary-gonadal (HPG) axis in larger biomonitoring species have not been developed for smaller species used in reproductive studies, such as Japanese medaka. In this study, physiological responses, including plasma vitellogenin (VG), hepatic estrogen receptor (ER), plasma steroids, gonadal-somatic indices (GSI), gonadal steroidogenesis, and pituitary function, were measured in mating Japanese medaka after 14 day exposure to 0, 0.2, 5, 500 and 2,000 ng/L ethinylestradiol (EE2) and correlated with reproduction and offspring development. EE2 was found to disrupt the HPG axis at multiple sites in male and female medaka resulting in depressed reproductive function at high doses and stimulated reproductive function at environmentally relevant doses. Fecundity was significantly elevated at 0.2 ng EE2/L, while fecundity, spawning frequency, fertilization and hatching were depressed at 500 and 2,000 ng EE2/L. These data correlated well with VTG, ER and GSI responses in both males and females, which could be indicative of EE2's ER-mediated mode of action. Generally, most biochemical endpoints were more sensitive to EE2 than reproduction or development indicating that reproductive function may be relatively protected.