TWENTY-FIFTH ANNUAL EASTERN FISH HEALTH WORKSHOP MARCH 10-13, 2000   Infectious Necrotizing Enteritis In Cultured Juvenile Summer The Pathobiology Of 17b-Estradiol In The Summer Flounder, Paralichthys dentatus     Doranne Borsay Horowitz, George Gardner, Ruth Gutjahr-Gobell, Lesley Mills, Romona Haebler, Gerald Zaroogian     U.S. Environmental Protection Agency, NHEERL-Atlantic Ecology Division, 27 Tarzwell Drive, Narragansett, RI 02882   Estradiol has been shown to cause increased vitellogenin (VtG) concentrations in male fish. The intent of this study was to evaluate the pathobiology associated with exposure to  17b-estradiol  (E2) on  liver, kidney,  and  testes of  summer flounder,  Paralichthys dentatus.   Juvenile male summer flounder were treated  twice,  two weeks apart,  via injection into a dorsal sinus with concentrations of 0.1, 1.0, or 10.0 mg/kg E2.  The 17b- estradiol  was incorporated into coconut oil to effect a slow release mechanism.  Control fish were injected with carrier coconut oil and handled in the same manner as the dosed ones.    At four weeks after initial injection,  a hyaline substance had  accumulated  in  a dose-dependent manner within the liver, kidney,  and testes of the 17ß-estradiol  treated fish.  Excessive hyaline accumulations produced hepatocytic hypertrophy in the liver and injury to glomeruli and tubules in the kidney.  These hyaline accumulations contributed to mortalities observed  in the 10.0 mg/kg  treatment.   In the testes,  the hyaline substance was  observed in  stromal  elements of  seminiferous  tubules  and ducts,  and  testicular development  was impaired.   The hyaline-like material  stained positively  with  Periodic Acid Schiff,  both with and without diastase digestion.  Immunohistochemical staining for presence of  VtG was positive in 17ß-estradiol treated flounder liver, kidney, and testes. No positive staining for VtG was observed in the control tissues.   Return to 25th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page