ENVIRONMENTAL-POLLUTION CAUSED ELEVATED CONCENTRATIONS OF ESTRADIOL AND VITELLOGENIN IN THE FEMALE FLOUNDER, PLATICHTHYS-FLESUS (L)

Female and male flounder, Platichthys flesus, were exposed to various concentrations of polluted harbour dredged spoil in large mesocosms fo r up to 3 years. The dredged spoil contained a mixture of contaminants representative of pollution concentrations found in the natural envir onment. Ovarian development, vitellogenesis and steroid hormones in th e fish were studied and compared with results from feral fish sampled at a relatively clean field site in the Dutch Wadden Sea. Plasma conce ntrations of vitellogenin (VTG), established by densitometry in sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) gels, f luctuated during the annual reproductive cycle of the Wadden Sea floun der and reached a maximum during autumn and winter (advanced vitelloge nesis). Fish held in the polluted mesocosm for 3 years exhibited prema ture vitellogenesis, resulting in a high number of oocytes in the yolk granule stage in spring, normally the previtellogenic period of the y ear. Moreover, VTG was significantly elevated in the plasma of these f emales relative to the concentrations in fish from the reference mesoc osm. The high concentration of plasma VTG in females from the polluted mesocosm coincided with significantly elevated concentrations of test osterone and 17 beta-oestradiol. The in vitro ovarian production capac ity of these steroids, however, was not altered. In feral and pollutio n-exposed male flounder, no VTG was detected. On the basis of these fi ndings, it was concluded that premature vitellogenesis in the female f lounder was a result of elevated 17 beta-oestradiol concentrations rat her than a direct endocrine effect of xeno-oestrogenic contaminants. I t is suggested that the elevated 17 beta-oestradiol concentrations are caused by decreased clearance rates of steroids in the blood. (C) 199 7 Elsevier Science B.V.