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GONADAL DEVELOPMENT AND ENDOCRINE RESPONSES IN JAPANESE MEDAKA (ORYZIAS LATIPES) EXPOSED TO O.P'-DDT IN WATER OR THROUGH MATERNAL TRANSFER
Citation:
Metcalfe, T. L., C. D. Metcalfe, Y. Kiparissis, A. J. Niimi, C M. Foran, AND W H. Benson. GONADAL DEVELOPMENT AND ENDOCRINE RESPONSES IN JAPANESE MEDAKA (ORYZIAS LATIPES) EXPOSED TO O.P'-DDT IN WATER OR THROUGH MATERNAL TRANSFER. Presented at SETAC 21st Annual Meeting, Nashville, TN, Nov.12-16, 2001.
Description:
In: Environmental Sciences in the 21st Century: Paradigms, Opportunities, and Challenges: Abstract Book: SETAC 21st Annual Meeting, 12-16 November 2000, Nashville, TN. Society of Environmental Toxicology and Chemistry, Pensacola, FL. Pp. p. 262. (ERL,GB R816).
Various isomers and metabolites of DDT disrupt endocrine systems and gonadal development in fish and wildlife, and o,p'-DDT has been shown to be a relatively potent estrogen agonist. In this study, we exposed Japanese medaka (Oryzias latipes) to o,p'-DDT using two exposure protocols: i) Direct exposure of early life stages to aqueous solutions from 1 to 100 d post-hatch, and ii) Exposure of female medaka to aqueous solutions, followed by mating with unexposed males to product offspring that were exposed through mechanisms of maternal transfer. In treatments with direct aqueous exposures, an intersex condition of the gonad (i.e. testis-ova) was observed in male medaka exposed at early life stages to nominal o,p'-DDT concentrations of 50, 10 and 5 ?g/L; indicating that this estrogen agonist can alter gonadal development when exposure occurs continously over the period of gonadal differentiation. Comparisons with previously published data on the induction of testis-ova by exposure to nonylphenol (NP) and octylphenol (OP) indicated that the relative potencies for induction of inter-sex in medaka are o,p'-DDT>NP OP, which is not consistent with the relative estrogenic potencies of OP>NP>o,p'-DDTobserved in the yeast estrogen screening (YES) assay. In the maternal transfer protocol, no testis-ova were observed in the offspring, although there was some delay in time-to-hatch of the offspring. Medaka exposed by maternal transfer showed no other toxicological responses during early life stages, but when treated fish reached sexual maturity, the females showed more advanced development of oocytes. In addition, when medaka exposed by maternal transfer were subsequently exposed at 10 mo of age to 17b-estradiol (12mg/L), there was a significantly greater induction of hepatic vitellogenin in DDT-exposed males in comparison to control males; indicating that exposure to estrogenic chemicals during early life stages may potentiate vitellogenin induction following exposure events later in the life of the fish.